well, fucking up a fim is pretty much impossible, as fim stand for fuck i missed, and was called so because someone trying to top their plants missed the whole top, and left some of the meristem behind, hence a fim, so long as you didn't completely take off the top growing tip, but took some of it off, you fim'ed it, lol, if you took the whole thing off, you topped it..
i think some strains take to fim'ing and topping better, but i'll probably get beat down for that opinion.. but to me, some strains only tend to grow that one top cola, with not much side branching at all.. if you read breeder descriptions and it says good strain for sog, this is what it mean.. so if you go and cut off that main top, i think you basically screwed yourself.. yah, now the lower buds will grow, but you just lost that one big top, and nothing below is going to get that big imo.. but anyhoo's..
lsting to me is the better option as the lower buds till get all of the same auxins that they get when one tops but you're also leaving all of the tops, not taking away any buds that maybe dominant..
i'd say in about 6 weeks or so, depending on the strains, is when you should get a pretty good idea of yield as all of the buds are pretty set at this age, they're still going to fill in more obviously, but you can get a better idea at this time... so i'd give them a few more weeks or so and post another pix so we can get a better idea...