A smaller piano might have a thinner, but more penetrating sound than a larger piano with a rounder tone.

There is a formula for determining piano size and room size in Larry Fines Piano Buyer. The way the piano projects sound does factor into what’s overwhelming for a room. I can more easily play whisper soft on a concert grand than my 6’ grand but when I play the nine foot piano super loud, on a tile floor in my great room, it would be overwhelming for my home and probably my neighborhood. That big soundboard projection might not be acoustically pleasing with my ceiling height and room size. I’m not an expert but really don’t think a taller upright should make that much difference and shouldn’t hamper learning to play softly.

It is not ideal to feel inhibited if you need to develop your tone. It also depends on the piano. A Yamaha U3 is not that louder than a U1. A German 130 has much more potential power. An FFF is the same powerful sound you would find on a baby grand piano. It is also easy to play to play softly even though you do not have the real uni corda pedal that a grand has.