On the cover, I just beat up this topic and bought one for a friend I helping with their camper. I narrowed down the brands to Adco and Classic Accessories. Then I went for more the better end ones, but not the super best. I wanted a warranty of at least 3 years, all weather fabric and the cost to be tolerable for the quality.
In my case, the front of the camper to the back bumper is 25' 7" which is the size I went for on a universal fit one.
Here is the Adco at RVUpgrades I was looking at. ADCO 34843 Designer Series Tyvek Plus Wind https://www.rvupgradestore.com/adco-...-p/01-0133.htm
And here is the Classic one, Classic Accessories 80-137-171001-00 PermaPRO
I went with the Classic one. It has 4 zipper panels on the door side verses 3 on the Adco. Getting into the camper in the off season is a need for my friend and the smaller panel could be easier to deal with. And the Classic has a better warranty. Again, keep in mind, warranty is important and the better warranty the better it will hold up, but a rip/tear may be what forces a change rather then being beyond the warranty. The cost up grade on the Classic was not that much more then the lesser cost on the Adco.
Your camper will have a shorter cover, and be a little less cost. I went with RV Upgrades as they have them in my size, at least now, and the price beat out many others. I have used RV Upgrades a lot and have had good transactions with them. Shipping is free over $99 so the cover would be free freight.
I ordered the cover yesterday, and surprisingly, UPS dropped it off today. They are Ohio based, so maybe that was way it came so fast. I have not used it yet, so I cannot report on that part. Give me about 3 weeks and I can report on the fit etc.
To keep mice out, the first line of defense is to plug up any hole in the bottom of the camper. There can be several places that invite mice in. Look real close "all over" the bottom of the camper where anything goes up through the black Darco plastic liner. Any hole in the black Dacro is a mouse entry point. If they find the smallest hole, they then chew at it and make it bigger then get into the basement and up into the living space if the can find a route to it.
I'm assuming you may not have the shore power cord plugged in. If it is not, that cord hole is an open invite to mice. Seal up the hole around the cable.
Do not leave any food inside.
As to blow out or pump antifreeze. I myself blow out, but I have done extra rework on the piping to make sure all the lines and pump will be blown out. And I use a big enough compressor to make sure it will blow it out. If you are not sure of the air blow out method on your floor plan, then pumping the anti-freeze through the lines does work, again if done right.
The drain traps need anti-freeze regardless of the line blow out method.
Hope this helps.