For a drivetrain with short chain runs, no chain tensioners are needed.
We had more issues with over/under tensioning, slipping bearing blocks, etc. when trying to tension the chains in years past. Why add the weight, add drag to the chain, make extra parts, when you don’t need them.
We also use US Tsubaki chain that is prestretched, that helps a lot also.
Don’t use master links, buy the new Vex #25 chain tool.
And there is no need for #35 chain so long as your sprockets line up.
We used #25 chains to lift the robot in 2016 with two CIMs per chain off a PTO, nuf said.
I will say that removing .018" of chain length for #25 chain worked beautifully for our Vex sprockets, but the 221 dual sprockets were a slight bit looser and could have used some additional reduction.
And chain in tube is fine if everything is done correctly.
It does scare me about rivet bits, screws on the field or a zip tie falling into the frame rails.
Here’s instructions on putting together a chain in tube chassis, might give you some ideas.
https://www.chiefdelphi.com/media/papers/3392