Which killer is best at Hit & Run playstyle?

Onyro.

I'd say Dredge.

Sadako is pretty good with hit and run

Wraith and Sadako are very good at it. Stealth killers are usually the best at hit and run because they have the easiest time landing that first hit.

The issue with hit and run is that one Circle of Healing completely destroys you.

Legion can get more hits while running, but I feel map mobility is necessary for Hit and Run to be successful.

Wraith is semi-reliant on how strong the loops adjacent to gens are, but he is solid. Stealth 6.0m/s is nice for mobility, but can still suffer when needing to go to the opposite side of the map. His power also can be used at many short loops to deny the pallet, but usually can be outplayed by Survivors. By that I mean it usually is their play to lose, as opposed to your play to win.

Sadako has a teleport location near each gen, but no meaningful chase power and 100s basekit CD on TP locations. Not the best imo, but she can get great value with A Nurse's Calling since her 24m terror radius is smaller than the 28m aura distance. Just be on the lookout for OTR and Shadow-Step.

Dredge is my personal favorite, and lockers are a little more plentiful than gens. This comes with a massive drawback on say farm maps, Haddonfield, Mother's Dwelling as a realm, among others, as each of those maps are very limited to lockers in good places. He also has at least some form of anti-loop, which is basically a fair version of Artist's. Ultimately though in many cases you will be reliant on winning 50/50s, so you need that Psych degree to get true value.

I have used the stealth add-ons for Demo and honestly that feels like a strictly superior version of Sadako. You get massive stealth but you have to set up portals in good positions so Corrupt is almost a must. Also when combined with the wallhacks Iri add-on you get intel for days and don't have to run any intel perks. His playstyle is heavily add-on reliant as the highest tier undetectable is the only one of value imo (Green .5s, Purple 3s, Iri 8s and silent arrivals). Overall it is a toss-up between Dredge and Demo for the most enjoyable imo.

One flaw all these semi-normal stealth Killers have though is they have very loud tells, so often it is better to play a non-stealth Killer with stealth perks instead. It is darn near impossible to mindgame without LOS with Dredge since Dredge is so friggin' loud, the Surv can echo-locate his exact position through walls.

The 2 best hit and run non-stealth Killers imo are Blight and Wesker. Blight has an add-on to make him undetectable during rushing, and Wesker with Spray usage oblivious on one and undetectable on fully infected on another. Blight is just busted OP in general so you can afford meme builds and win without trying against the majority of matchups. Both of them also get decent value from Plaything to make everyone oblivious. This also can help to counter Stakeout Hyperfocus if you are worried about that. Wesker also gets value from repeatedly infecting and leaving Survivors due to the limited Sprays in the match and the permanent Hindered+Power Exposed.

Overall the best killer for Hit and Run is the killer you enjoy playing, since you will also know how to counter them the best when playing as Survivor as well.

Legion seems like a no brainer since its literally their power.

Wraith is good at it too considering he can zoom around the map cloaked, especially if he has windstorm.