Never used them sticky but I do freeze left over maggots to save for short sessions where it’s probably not worth the expense of getting new bait, especially in winter. It picks up fish but not as effectively as live maggots in my experience.
Yes you can use sticky mag on a feeder, I've used it on a method casting 30 or so yards to under trees for tench. Also made little balls and used them using a catty. So using them in a pellet feeder is perfect.
Yes it is a viable method in a pellet feeder as long as you don't press the sticky maggots in the feeder to hard. You'll soon know, as you'll be bringing the feeder back with the sticky maggots still in the pellet feeder.
A water we fish in the colder months responds very well to dead maggot in the pellet feeder. But after a lot of experimentation I've found it best to feed just dead maggots with the pellet feeder capped of with an crushed expander type ground bait or just a few micros....