I have mine in a 48x18" tank and will be upgrading it soon. they like space, they don't like open space with no hiding spaces. they like to feel hidden and secure. so my rule is to always go as big as you can, just build it for the intended species specifically.
basically any of your typical tropical house plants will work. looking at the biodude or neherps should give you a good idea.

yes your uth will be useless on the bottom. on the side it doesn't really do much other than to block heat escape from that side and keep the temps up a few degrees above ambient at <5" from the uth. basically all but useless. and as for what will work or if the Che is enough, that depends on your tank, the scape, the ambient temps in your house and so on. you playing around with it will be the best bet. also make sure to use a thermostat and digital meters.

120v is standard u.s. plug voltage. the w is what is key here.