From my personal and recent experience, I would buy any frame that has a reasonable geometry at a reasonable price. Don’t sweat the details at this stage as it will take a while to dial in your fit and position for track as it’s very different to the road. You won’t know what you actually need until you have ridden a particular frame for a while and realise what you need from a frame geometry that can’t be changed with stems and bars etc.

when I first started looking into track frames I was attracted to much more expensive and good looking frames such as the Cannondale Caad10 or the BMC TM01.
Thankfully I purchased neither and went for a Planet X. Was the Planet X the best frame? No, not really, but it was definitely good enough to compete on and it allowed me to find out what I wanted from a frame. As it turns out the caad10 and BMC would have been totally wrong and I would have wasted money. Thing is they were about £1500 whereas I only spent £350 on the Planet X. I have now swapped the Planet X for a Dolan DF4 but I’m glad I had the PX To find out what I needed before dropping big money and I can sell the PX for pretty much what I paid for it.