Good timing to think about this before the blast rather than after. Finasteride works by blocking 5-alpha reductase which converts test to DHT, so yes it helps on a straight test cycle. But you are right about DHT derivatives, compounds like masteron, winstrol, anavar are already DHT based so finasteride does nothing for those, you are not blocking a conversion that is not happening.
The coming off question is tricky. Finasteride does not restore hair that is already gone but it can slow or stop ongoing loss. The shed you are seeing at 7-10 hairs in the shower on 200mg cruise is pretty mild honestly, most guys would not even flag that as concerning. At your age with a full head of hair the smarter play might be minoxidil topically rather than systemic finasteride. Lower side effect profile, works locally, and you are not messing with DHT systemically which has its own implications for mood and libido on cycle.

Finasteride is a nuclear option. Oral Fin fucked me up for about 8 months after i stopped taking it. Not super common, but holy shit. I use a compounded Topical Fin @ 0.05% YES 0.05% now and it doesn't tank my Serum DHT at all. zero sides, also doesn't work as well. i take oral minox daily.

be care with that fin, it can have some wild side effects than can even last years after you stop it IT CAN EVEN MAKE YOUR DICK SMALLER. be careful playing with that f!re, you might get burned. your safer trying the RU stuff.

I use the topical finasteride / minoxidil spray. I think it really helps. I am 56 and have started getting thin up top. I think I am just holding back the tide and probably a losing battle, but so far it isn't apparent and has stayed that way for a couple years. I do not get any sides that I am aware of - though I have been on a couple larger intermediate cycles plus ancillaries so a lot going on, hard to be clear on what any sides are coming from. However, I recommend it. Kinda pricey through HIMS though, like $195 for 3 month supply.

edit - yeah I heard the same thing regarding DHT derivatives. I was on a large amount of mast recently (until it crushed my estrogen and my cycle sank into the abyss), and my hair amount didnt change. Though maybe if I had stayed on it for longer than 5 weeks it would have started.

always better to be safe than sorry. Nizoral twice a week. Lather up and leave it in until you finish your shower. Just keep it out of the eyes. Also great for Bacne

If your father was going bald when he was young ..... then you will too just like I have.

If MPB runs in your family then taking Steroids will speed it up again like it did with myself.

HOWEVER, if you have thick healthy hair and your father did till he was old - then you will likely be fine.