Nobody can tell you what is best for you. You need to figure out what heat source the new tank needs by running it.

I would set it up with the che and see what it gives you. Leave your snake in its tank until you get the new one dialed in.

I like che and I like using them with the Zoo Med lamp stand. They allow you to point the che and raise and lower it to the desired height.

If you want another bulb for light alone you could always add a led bulb.

You said you were adding a lining but if it were me Id put the insulation on the outside instead.