I *really like* using an adapter that lets me drop in nice, small CPL and ND filters behind lenses like my TS-E 17 and 11-24, instead of the front filtering options for those lenses that are, respectively, salad plate- and dinner plate-sized.
With my current lenses I feel happier having a good quality protective filter on the front, but yes, that isn’t really an option for the 2 lenses you describe, so I can fully understand the value of an adaptor with a slot-in rear filter.
I’m not so sure of the value of the adaptor with the control ring though - it must feel a bit odd switching back and forth between adapted EF lenses with the control ring at the rear, and RF lenses with the control ring at the front. I’m sure there are some people who find the control ring adaptor useful, but on my RF lenses I’ve disabled the control ring as I find that there are more than enough customised dials and buttons already for my needs.
Currently I’m using a mix of adapted EF lenses and RF lenses, and I’m likely to continue using some of my EF lenses (e.g. 24mm TS-E, 100mm IS macro, 180mm macro) for several years. Potentially using adaptors can introduce a small amount of play, and increase opportunities for the ingress of moisture, although I haven’t experienced this myself. At one stage however I did have a 1.4x iii extender which introduced some disconcerting play/wobble when used with my 100-400mm Mkii and 300mm F2.8.