I have a Phal that I rescued from one of my Daughters. It is about 5 years old and looks like its all roots bound in a 4" X 4.5" container. This one has"Only" been watered and never has been re potted with new potting material.
Now is it possible to "Thin" down the root system by cutting off some of the roots or some that don't look so healthy. I can if needed post a few pictures if needed.
Pictures could be helpful but in general it's best to leave as many roots on the plant as possible. Selecting a larger pot that can accommodate the root system is always preferable to cutting off functioning roots.
Ok here's the root mass. After 5 years without a re potting 99.9% of these roots are good, didn't find any dead roots from the main plant it self just three tips of the roots needed to trimming off dead part of them.
Phals are perfectly fine bare-root for a long time. Just be sure the roots get wet every day or so. It's fine to leave it bare-root until you find the right pot.
__________________ May the bridges I've burned light my way.