Sounds pretty. You don't have to pinch them back unless you want to. When you pinch them then they will just make another branch. I don't usually pinch mine back but my alata got the top broke off by the wind and it just made one other branch and kept growing up.

People have diff. ways and preferences on fertilizing passiflora. I do fertilize mine once in a while. Some people add banana peels also. When I fertilize, I just use a little bloom booster, epson salt, and superthrive. I gave them a foiliar feed in the spring of the spray n grow, bills perfect fertilizer , cocowet trio. You do not need to fertilize all that often because they can grow in poor soil. Make sure they are well watered before fertilizing.

You probably shouldn't use a lot of high nitrogen fertilizer because you will get a lot of vine growth and they may spend their energy on foilage instead of flowering.
~SJN

I have a similar situation. My passiflora is growing taller than the trellis. Should I pinch it back? It is a first year plant so no blooms yet. Can I train it to grow back down the trellis? Thanks in advance!

You can train or pinch. I don't like to pinch, because sometimes it takes longer than I'd like for new growth to start elsewhere on the vine.

I read somewhere that passiflora will grow "up" until the vine can't grow up anymore and begins to hang down. Once it reaches this point, that's a signal for the downward parts of the vine to start sending out radial sprouts. I've got a citrina that invariably send out new growth at the apex of vine this way.