The CT SYS capacity is really small (3.5L) and bags are $4 a pop. Contrast that to the "standard" 25-35L setups, you're looking at 7-10x the replacement schedule. It takes me probably two weekends of heavy sanding to fill up the 35L bags, that'd be $80 in bags/month!
The other option is to grab the $80 long life bag, which if they're anything like the CT 26 long-life bags, aren't super impressive. They're made in China, stitching is single stitch and pretty messy to boot. At the price, it needs to last 20x as long as the single use fleece bags, which they might...but it would be barely.
Rated power on the CT SYS is meh, it's on par with what the old CT MINI did, but the full size ones still pull about 50% harder.
I'm willing to bet you can find a happy medium between 16 gallon and .9 gallons.
I've had the Festool CT26 and the Starmix 35L, and both are of reasonable size. I can bring it in-out of the house fine, with one hand. Fits through doors fine.
The Fein no longer has motor control; suction is controlled via a port at the end of the hose. Bosch switched from Starmix to Karcher recently, but they both have been making vacuums for some 50-odd years. They should be available during the 20% off sales that should happen soon. Don't forget the Makita either, which is a Nilfisk product (who manufactured Festool's vacs until a few years ago when they decided to make their own); they've also been in the business for quite a while.