I am not expert at all and not sure if this helps...but I did root pruning on big ficus Benjamina (approx. 7'tall at that time) that was in same pot for quite a few years and never root pruned. I blasted the root ball using garden hose, and it took quite some time. I did have a big bucket full of water handy, but didn't really soak that much. Used bucket to keep it moist. I do not have photo of it out of the pot before washing, but roots were really big mess. Here is photo after most of the soil was washed out:

Whether to bare root and the extent of bare rooting a plant depends on the plant. I have found that some plants survive bare rooting well while others do not.

I have never bare rooted a rhododendron.

@Vladimir they say to never expose rhododendron roots to the sun, but I really don't understand how else you could do it.

Sod-like ones like rhododendrons I don't mess with much. With such densely rooted kinds - or others I don't want to fiddle with - I may just cut through the center, to stop circling and leave it at that.

You DO want to hang onto as many roots as possible, are cutting some of them only to prevent girdling or toppling of woody subjects later.