Wanting to increase cardio output, but the you asked about protein intake.

More protein isn't necessarily better. I've been about 120g protein each day I lift (3x/week, all at home cause I hate gyms, all with dumbbells) and about 100g the other 4 days (two of which are cardio, usually trail or road runs but sometimes HIIT, I take Th/Sun off). I've put on 12-14 lbs of muscle with my weight staying the same (~168) in 7 months without impacting my cardio (I ran before, distance and pace is essentially unchanged).

I rarely do cardio and lift on the same day. I don't pound protein. I don't use creatine or pre-work out, but rather get all my protein from protein-rich foods. Energy levels up despite not eating an otherwise super strict diet...I want to do something sustainable, not that makes me miserable.

I'm no body builder (not trying to be) nor Ironman (no time to be). But I suspect I'm probably in better shape accounting for strength and cardio than 90% of guys on the board and 95% of the population. Really tough to be super strong or super fit from a cardio standpoint. Some guys pick one or the other. I feel what I've done has managed to be a good balance of both.