tub install with tile surround

Hey, new member here with a couple of questions about my bath remodel.

1. As long as my measurements are accurate, and I dry fit my tub & connections, is there any reason to not have the plumbing all in when I set the tub and connect my drain and overflow after its in?

I'm installing an americast princeton tub and i read that it voids their warranty for some reason?

My drain and overflow will be all glued connections.

One other thing I'm dealing with is a floor joist exactly in the center of my drain. It was already notched out for the drain tube, but for the overflow I'll be putting two 22 1/2 degree connectors together to get the overflow tube over the 3/4" I need to be centered. That is how my old fiberglass tub was plumbed so should be Ok.

2. I read through some other posts and saw someone here suggest running the tile backerboard over the tub lip, but leave 1/4" gap at bottom and silicone the gap before doing tile work. Is that what most of you would agree with?

I've seen others suggest running backerboard to just above tub, sealing with silicone then thinset and tile down to tub. They said it prevents water from wicking up the backerboard and getting behind wall. So I'm perplexed on using which method?

Thank you!

Offset the overflow is okay by me. I just did one like that on Friday.
I should of snapped a couple pictures of it.

Here we are required to use peel and stick flashing over the tub lip then paper all walls before installing hardibacker of wonder board

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The two couplings worked great to line up the overflow drain. I used masking tape to center my drain measurements. That worked out perfectly to line up the drain to know how long of a pipe to the drain I needed.

I decided to run backerboard to just above tub lip. Running over doesn't keep it flush and plumb against the framing. I'm going to silicone the heck out of the joint. Then water proofing all of the backerboard with red guard.

Thanks for the tips!