... I will probably go with Woodcraft since there is a store close by and I need to make a trip there anyway.

Do I need to thin this out? Or does it go on full strength? ....

Not necessarily. I usually make my first coat a 50/50 varnish/thinner
mixture. That acts almost like a prime coat. I did buy the Behlin
thinner, but I think that (less expensive) ordinary thinner works just
as well. I was just playing it safe with commissioned piece. Maybe
someone at Woodcraft may know the answer.

... I haven't worked with varnish much....

so far, I've used Rockhard on two tables. I doesn't self level as
easily as most varnishes, and it's best to wait a while before
rubbing, if that's what you plan to do. See if you can get hold of
Jeff Jewett's video. There's lots of good information on varnishing.

Good Luck ---

Joel