In all honesty, you just need to practice with them. Learn their strengths and weaknesses. Not to be cheesy, but BECOME the character. Practice till you can just feel where the blink will land. Practice till you can navigate an entire McMillin Estate map with your chainsaw sprint.

Map wise, Nurse ANY, Billy, Coldwind and McMillin are best, IMHO

So if I'm correct, you are asking for any perks or addons or such that will directly help you improve using their abilities, i.e. landing blink attacks and chainsaw hits, not necessarily just good builds that will help you win overall, right? If so, I don't imagine there are many perks that would directly affect your personal ability to get hits besides maybe stealth perks that can get you up close to them. Besides, stealth perks aren't these killers strongest options (aside from maybe tinkerer).

Although most of these will not drastically change your skill requirement, some addons will give you more opportunities to get more chainsaw or blink attacks, particularly cooldown recovery addons or addons that let you use your ability more often.

Nurse has:

Wooden horse (common): Less fatigue for missed blink attacks

Dark cincture (uncommon): Reduces blink recharge

Catatonic boys treasure (uncommon): Decreases fatigue caused by chain blinks

Fragile wheeze (rare): Reduces blink recharge

Ataxic respiration (rare): Reduces fatigue

She also has plaid flannel (common) which shows your blink location. Some people find this helpful to learn her better, which would help you land hits, but I would personally recommend against using it frequently.

Billy has:

Junkyard air filter (common): Increases overheat limit

Dad's boots (uncommon): Increases steering

Punctured muffler (uncommon): Increases cooling rate

Black grease (rare): Increases cooling rate when a flashlight is shining on you

Spiked boots (very rare): Increases steering

Billy has no alternative to plaid flannel

Keep in mind these are NOT necessarily their strongest addons and a combination of these addons will NOT necessarily be their best addon combinations. These are just the addons best fitted to assisting you with your question (or how I perceived it) - 'How to land more chainsaw hits and blink hits'.

So there are some perks and many addons that will give you more opportunities to get hits, however, even though they will all give more chances to attack, I can't think of anything of the top of my head right now (although I'm almost certainly missing something) that will directly make you blink attack and chainsaw people more often and more accurately to a substantial degree. So with the exception of perhaps billy's steering addons that give you more turning freedom, in the vast majority of cases, your own personal skill with that killer is what will get you the hits, not the addons or perks. If you are bad with nurse and can hardly land any hits; you putting on 2 addons and some strong perks is not going to instantly make you better at landing hits with nurse, as with billy. So play around with addons if you want (although both killers are very non-reliant on addons) to see if anything works for you, but honestly just general practice will help you get more hits, aka. getting better with their power. If you have at least 1 friend who owns the game, go into a custom match on the most open and clear map you want (I recommend Blood Lodge as a good one to just test things on), and practice. Learn billy's turning speeds and how his chainsaws hitbox works, practice curving around cars, try chasing your friend/s. Try learning how long you can blink with nurse, how long you need to charge a blink, what you can and can't blink through, etc. If you don't have someone to play with, if you have 2 platforms (so like a pc and a ps4) you can go into a game with yourself. If you can't do that, might need to just do it in normal matches.

TL;DR - I probably misunderstood your question as "what perks, addons, maps, etc. will help me land more chainsaw hits and blink attacks", but if I didn't - Perks, addons and maps will certainly help you win a match overall and make you stronger, but very few will directly make landing ability related hits easier and more efficiently, that is just left up the players personal skill with that killer.

Probably a lot wrong with this, do correct me on all the things I know I got wrong