Unless good fit and form are used, the youth models tend to be hard kickers. Besides the lighter weights, the shorter stocks tend towards smaller pads, thus concentrating the kick's energy in a smaller area.
Since you have shotguns already, I suggest you work with those to better handle the weight and recoil.
25 mounts a day will accustom your muscles to the weight better, light loads will kick less and still do the job.
My bird 870s run 7.25 to 8.25 lbs. Using them at clays with milder loads tune and tone my muscles and the kick doesn't bother me except when patterning turkey and waterfowl loads. At trap, the most precise and longest range clay game, 7/8 oz loads give me the same breaks and scores as 1 1/8 oz loads do. Use light loads whenever possible, modern ammo has more bounce to the ounce with hard shot, one piece plastic wads, etc...
My slug shooters double as "Serious" shotguns and they run 8.5 to 9.25 lbs, IIRC. After long use, they handle like 20 gauges and there's little kick with standard slugs and 9 pellet 00 loads.
However, if you want a 20 gauge, far be it from me to discourage you. It might not be what you're looking for though.
HTH....