Advice for learning Clown and Bubba?

For both Leatherface and the Clown, I would recommend ruin, or another game prolonging perk, as they both lack the map pressure that some other killers possess.

The Clown's ability forces survivors to drop pallets earlier than they would when facing another killer so using either enduring or brutal strength to help deal with pallets is very beneficial. Enduring, in particular, is one of my favorite perks for the Clown as it can help combat decisive strike. If you drop a tonic on top of a survivor who has DS, and then you grab them and get struck, not only will enduring help you recover faster, but the survivor will get intoxicated from the bottle you threw and be unable to make much distance before you catch up. If you have the room in your perk set, running spirit fury with enduring can be a deadly combination.

With the Clown, hitting survivors directly with your tonic is less important than forcing them to go where you want them to go by using your gas cloud to control their pathing. You want survivors to be in a position where they have to choose between getting intoxicated or moving towards an unsafe location. Additionally, If you see a survivor running straight for a window make sure to throw a bottle in their direction as they will be unable to fast vault while under the effects of intoxication and the forced slow vault will give you an additional opportunity to hit them.

Unlike the Clown, Leatherface has fewer options for slowing survivors down at pallets, so you will need to chase them until they drop it. If you are using good addons, your chainsaw can help force survivors to drop pallets earlier, but that is still situational. Similarly to the Clown, using enduring to eat pallets can help get through them faster and combining it with spirit fury can be beneficial.

Like many said. LF isn't able to use his ability on pallets or loops that well. He is all about positioning. When you have to destroy a pallet on a loop, I like to use my chainsaw for it. It allows you to avoid flashlights while charging or keep an eye on the survivors route. Also sometimes it's smarte to break the pallet from a side, which lengthens their path to the next vault or looping spot. Mostly, if there is a chance to chainsaw them going there.
Survivors seem to like to jump into a locker to dodge your chainsaw, but that's not efficient, if you bump against it. You tantrum is lethal and when it stops, you can grab immediatly after.

Besides that for perks. Depending on the map or situation, TInkerer might be a good choice. Sometimes brings you very close to your victims, which leads to chainsaw hits, by my experience. But it's not a must. I jus think it's a very fun perk on him.
I like to play him as a pallet destroyer. Charge-Addons+Enduring and Spirit Fury, helps you to clean the map from safe spots. LF is also good to ignore unsafe pallets and destroy them later with the chainsaw, to recharge SF again.

Something like Ruin or Sloppy Butcher help you to stall the game. BBQ is still quite good to get a little bit oversight, what people are doing, but you can play without it and maybe choose a tracking perk like Whisper instead. But really it depends on your taste. Certain good chase perk, work all well on him on my opinion.

@Poweas

Clown:
When a survivor runs into a jungle gym, throw the tonic in the middle.

When a survivor is looping a pallet, throw your tonic down on the LONG SIDE of the pallet, and force the survivor to run through it or abandon the loop.

This mean this: Every pallet loop has 2 sides. Good pallet loops will have a long side (a path that takes longer to run around) and a short side. (A side that takes very little time to go around) Bad pallets have 2 short sides. And "God Pallets" Have 2 long sides. (think killer shack, or anywhere the killer HAS to break the pallet)
You throw the tonic on the side it will take the longest for them to get back to the pallet, and make them take that path. If placed right, the smoke will cover most of the loop, giving you a hit.

Save your tonics for loops, if you aren't great with throwing them.

You shouldn't try to hit people with the tonic You want to overthrow, and make them run through it. This is because:

1: It's slow and will probably land behind them. And even if you hit them...

2: The slow doesn't last long after they leave the smoke, so the longer they are in it, the longer the slow. Which means, you will gain on them more, if they have to enter the smoke.

However, survivors wont want to enter that smoke. So it's absolutely great at herding them.

Try this: Next time you are chasing someone from one loop to the next, fully charge your tonic, and hit it against the next loop they are running for. I bet they break off and go for another loop. This should give you the time you need to hit them.

This has been "Clown 101" from Learning to Kill

edit: One last clown tip:

The clowns intoxication can slow survivors down enough that they SLOW VAULT windows they should FAST VAULT. Use that little bit of knowledge to your advantage when you can, but don't go overboard.

You like the thicc bois huh?

Lots of good advice here. Basically like most have said don't throw bottles at survivors throw them where you don't want them togo ie. Loop. Try maximize the slowdown. Don't throw it at the pallet where they will only be slowed for a fraction of a second before dropping the pallet. Throw it so you can maximize the hindered effect ie. far end of loop. Clown is the strongest m1 killer imo.

All Clowns add ons are good. Probably the best is extra hindered + exhaustion. When starting out maybe larger area + reload speed/extra bottles

LF is really basic. His saw sucks without add ons. All you can do is get on survivors but and charge saw if they dont get to a loop/window.

He has 2 decent add on combos. Carburetor + Beast Markings or Carburetor + Primer. I prefer the first for downing survivors but the second also breaks pallets quick. His Chili add ons are useless just ignore them.

For both stay away from mobility perks ie. tinkerer and pop goes weasel. Sloppy butcher is ok on LF since the perks applies to his saw.

Clown is super fun and a 1v1 machine. LF just is meh unless your into camping.