Would NOT limit Plant growth by smaller containers! Yes "Feeding" is more than necessary because of your "soil-less" mix!
"relying on summer sun" while in Pots? Tricky! However even in the best scenario, you've bought yourself the need for more attention to Plants;
v/s an "Outdoor Grow"..Please start em now at least, Not too late! You've still got 3 solid months of 'good' growing weather!
Would NOT be trimming young plants Bro! Let em grow, only trimming off dead growth! Good Fortune!