I would spool either of them with 12 lb mono and then get a 3/8th oz weight or casting lead. You don't want to start to light or too heavy with a casting reel. The mettle has more bearings and should be longer casting but the lesser bearing Casitas might be more forgiving right now.
it's really all in the settings.
with the casting weight tide on.. (or gold spoon or spook junior)... tighten the knob on the right snugly. This is the Spool Tension Knob.
Then depress the the spool release, if you've done the first part correctly at this point the line should not come off the reel. Without a thumb on the spool slowly untighten the spool tension knob until the weight or casting object or lure just starts to fall. For you I would retighten it about 1/8th turn tighter than you just loosened it. In this position it probably won't let line go off the spool in free spool but this will help you on your first several cast not get a backlash.
Both of those reels should be centrifugal casting brakes as a base. I would open the left side plate and set the real for 2 brakes to be engaged to brake when casted. You'll figure it out quick as the others will be clicked into a position where they will not run out to the end and engage with the braking surface.
With two brakes set and the spool tension knob slightly tighter than free spool, you can now make your first cast. The the cast is shorter than you like and you didn't feel any reel loops come up from the spool, then loosen the spool tension knob about 1/16th turn looser.. some of these have click settings... if so one click looser.
Cast again. This time begin to lightly touch the spool with your casting reel thumb during the cast... this is called feathering the spool.
You'll eventually lighten the spool tension knob and the go to one brake while feathering the spool and that's where you'll get your best casting performance. Don't let backlashes get to you, you'll always get a few 'professional over runs' even as an expert.
From here it's just practice. I'd stick with mono for a couple months and stick with the mid weight lures between 1/4 oz and 5/8th oz. I'd stay away from 1/16th heads with plastic and there's no real reason to throw a super spook right now and into the fall