I presume many people use a shorter length of LMR240 (or equivalent) and then switch to LMR400 (or equivalent) for the run to the radio.  So I am just trying to determine the length of those short jumpers at the antenna.

Would 15’ be a good length?

What about connectors?  For UHF side I will use N on the coax.  

On the VHF side, instead of a barrel adaptor connecting two PL259s, would it make sense to go VHF antenna -> 

PL259 - coax jumper - female N -> 

male N - coax to shack - male N -> 

female N - coax to radio - PL259 

Or is it fine to leave them all PL259 / SO 239?