There are quite a lot of frogs to choose from

If you like tincs I mentioned my approach to "sizing" in another
thread. BYH and Robertus are pretty big and you would have to take their needs into modifying the enclosure to make it easier for them to climb (e.g. more branches / ledges). If you want to go the tinc route, IMO this tank is better suited to dwarf tincs like Bakhuis, Oyapok, Nominant, Lorenzo that run in the 30 to 35 mm SVL range rather than 40 to 60+ mm for larger tincs.
Always go with the frog that you really like, then plan your viv(s) around that. You could always start with some larger tinc froglets and grow them out in this viv and see how they do. So if it's Robertus, then get a few froglets, start growing them out, and see if you need to plan a different viv. If you are looking at the WC pairs currently being offered, I'd consider a larger viv, and the risks / testing / QT regiments required with them.
I'll leave the thumbnail question to more experienced tiny frog folks. I just have my lamasi / Tingo Maria, which are a lot of fun and a family favorite. They are likely a good choice as well. You really need more vivs
