JTree ratings compared to yosemite?

Headed to yosemite for a hiking trip but will have one day for climbing, looking for a moderate multipitch, but should probably get acquainted first with some single pitch routes. Never climbed in the valley before, trying to gauge what difficulty I should shoot for.

I climb in Joshua tree and lead around 5.7 there, are the grades roughly similar for anyone who has climbed at both?

I have been looking a few climbs (munginella, the grack) but think it would be wise to try some single pitch climbs at 5.6 or so to get myself acquainted with the rock.

Any recommendations for areas with some easier single pitch climbs I can use to get myself familiar that also may be near a decent multipitch climbs nearby? I have been looking into swan slabs atm.

If you lead 5.7 at J-Tree, you'd be fine leading Munginella and The Grack, Center. You should get right on those first two, if you're wanting to do them. You could do them both in a day, provided it's not too hot! Start early on Munginella, to beat the crowds (rockfall hazard from climbers above) and to beat the heat.

Glacier point apron has plenty of moderate single and multi pitch stuff right there nex to the grack and further north.

The rock is pretty different (granite vs. monzonite), so even ratings that are similar can seem different because you may be more familiar with the coarseness of JTree but then the smoothness of Yos might make the rock seem like there is less friction.

Having done those climbs and also JT a fair amount, seems like you should have no problem with the climbing per se, but Swan Slab Gully is described by ST as a good introduction to the rock and I tend to agree.

Swan Slab

Both areas use the YDS so shouldn't be hard to make the transition.