Eric,
My system is fully exposed. Clean-out is at the coil
The top cap is removable and it allows snaking, but more likely serves the purpose of pouring into it a mixture of bleach & water to kill the mold buildup if it occurs. Never had to use it, but it's there. I had to use an offset to make filling / snaking easier. The bleach / water mixture kills the mold and it washes right out of the line.
Drain plug is in the low point of the system. You could find the condensate in the wall, put in an access panel and install a cleanout and / or drain plug. Doesn't take much to do and makes life a lot easier should there be any issues down the line. The main issue with condensate lines, I've come across is that they're too small. 3/4" lines work great in short runs, but long runs that last (at least that I've seen put in in some of the condo / townhomes here) were 3/4" pipe which dumped into a 1 1/2" pipe inside an outside wall and to the exterior. They never had any problems there and most of those units were well over 20 years old.
I open the drain plug at the end of the season and drain all the water out. I leave it open until the heating season starts then close it off again for the next year. I only have a 80% efficiency unit, so it doesn't produce h20 during the heating season.
I put these in place 10 years after the install. The original condensate lines clogged up and flooded the laundry room. I swore that it would never happen again.... and it hasn't.