Many controllers have an octave selection key so you can play lower notes on the keyboard still by selectin lower octaves. (or higher)
If you’re wanting to “play piano” with both hands, a 49 key is the bare minimum and you’ll likely find as your playing grows, that you’re missing out on a lot of notes. If you’re looking to supplement what you’re doing in Ableton by jamming along with one hand, a 37 key should work fine for you. If the price difference and functionality set is similar between a 37 and 49, and you can find the space for it, go bigger.