What To Do With 2nd Tank

My LFS (a branch of MA) has sparkling gourami in from time to time - they tend to be in the same section of the LFS as the micro/nano-sized species; if you have a local MA, they may be able to order them in for you or let you know when they have them in next. They are quite timid, though, so I'd advise keeping them with the ember or lemon tetra from your more recent shortlist - other tetra species may be too lively or nippy for them. Cories ought to be fine with them, though. That would make a nice combination - sparkling gourami in the upper level of the tank, a shoal of ember and/or lemon tetra in the middle, some cories on the bottom level of the tank.

They rant really fussed as far as I know. They are very peaceful. I have had anything from 2 to 4 in the past personally but don't let that really strict you.

Usually.
There are three gouramis in the genus Trichopsis, and while all three can be called pygmy gourami I have only once in 20 years seen anything other than T. pumila, the sparkling gourami, in any shop. I have seen sparkling gourami labelled as croaking gourami - that name should be applied to the other two species, but shops will be shops when it comes to names.

Would bolivian or royal rams be an option? Or Harlequin Rasboras?

Bolivian aka royal rams would be OK if you have sand on the tank floor. But you need to be aware that if you managed to find a pair and they spawned, the cories would never learn to stay away from the eggs and could get picked on.

And with cichlids you need to buy a bonded pair or a single fish. Just any male and any female could well dislike each other. They are very difficult to sex when young - the only 100% sure way is by their breeding tubes which are not visible in young fish.

Harlequins would be fine. There are two similar related species, Trigonostigma espei and T. hengeli that would work as well. Harlequins also come in a colour morph that has a very dark body and an almost orange nose - this is called purple harlequin, black harlequin or royal harlequin depending on which name the shop decides to use.