Hi, welcome!

It sounds like you and me are in a similar boat. I just got back into the hobby, thought nids would be awesome, bought a bunch and am assembling/painting like my life depended on it!
I like your mix, looks like a very well-balanced army at the moment. As for biomorphs, I'm no expert on that- but I'd recommend feeder tendrils for your genestealers (gives you preferred enemy, reroll to hits for them and nearby units).
Do you have a reason for splitting the hormagaunts in two? Just from rolling it out with the odds, it seems like whatever is left from 12 actually making it into a marine squad... they might have trouble taking it down. 24, on the other hand...
Same question about your warriors, you've got them grouped 5/4/3 but I guess there are an infinite number of other combinations you could do, like 6/6... and again in
CC they'll make a bigger impact that way. If it's to divide your fire more evenly, I understand, but maybe just focus on making one more "shooty" group of warriors (enhanced senses, ext carapace, toxin sacs) and one "assaulty" group. That way, you can have the assaulty group run instead of fire and keep up with your gaunts... otherwise, they're going to fall behind. If you want to take 3 squads of them, I'd make the assaulting group the largest, rather than the other way around!
If you don't want a tyrant, with 2-3 carnifexes,
IMHO you don't need one! But if you get one, maybe you should drop a carnifex and focus on adding more warriors, since that's what you like anyway, and you've got plenty of screening units for them at the moment.
Just my $0.02