With small tracker speed is your best friend.
I have one of these (a Polarie), and in the last months have used it mostly with a tiny refractor at 300 or 230mm (usually at 230mm because the reducer ensure a large advantage in term of speed, ca 1 stop, meaning I can halve the integration time, and because, since use an aps-c sized sensor, feel that at 300mm the field starts lacking somewhat in width).
With a good alignement to the pole should be able to attain 120 to 180" subs, and keep most of them: in my experience this is adequate for most targets from fairly dark sites to avoid overexposition (it could be too much from light polluted sites, but in this case could keep shooting at 120" with the help of a LP filter).
I do not know what you mean by "learning indoor", as the only thing you could learn indoor is how to process your data: to align to the pole and to aim the tracker is something you can learn only under a (possibly dark) starry sky.
The good is that both the alignement to the pole and the framing are rather fast procedures, and once done you can simply go back to a warm place until the next morning (if am not stargzing, I set the alarm after a few hours to check, and eventually replace, the camera's battery)