In or out 90 degrees?
V-notches are fine...all depends on how you slide it in...
On my inward 90s...I made a simple v-notch for the corner....on the outward I made a wider v-notch...
So really it doesn't matter...also have a glue gun on hand just in case... A little goes a long way.
( I had a couple of spots that were aggravating, and I used hot glue and it is sitting pretty)