Gapping questions

by Matt
(Dayton Ohio)

My framing before decking added

I’m about ready install timber tech pro and I’m concerned about gapping. I have a few qts:

1. I have watched many videos and looked at many photos and it seems that gapping at the ends of boards between a picture frame are consistently different. Should I gap at both ends against the picture frame or make it a tight fit. Also, if I gap how to I keep the gap line consistent board to board? Is a track saw the only way?

2. I have seen many inconsistencies with corners. I would like to miter the picture frame corners but after listening to Dr Decks videos and other pros they say don’t do it bc miters always come apart. I’ve seen a couple videos gapping the miter at least an 1/8”. Is that that a good way to go or should I just square the ends and make a simple butt joint.

I’m trying to make this simple but I want it to look nice.

Any help is appreciated!