I’ve used Rodent Pro for several years because they consistently had the prey item sizes I needed. They do not vacuum seal, just put in freezer bags. As mentioned, they have flat rate shipping. I’ve never had a problem with them, though my last batch of rats had a strong smell to them - not off, just like the cages weren’t kept as clean as prior shipments.
I decided to try Cold Blooded Cafe for my last order and I’m pleased with the quality of the rodents. No strong odors and everybody is chowing down on them just fine. Prices were a bit cheaper than Rodent Pro for the items I ordered. They don’t vacuum seal either, rodents just come in freezer bags. They also have flat rate shipping.
I’ve also used Layne Labs in the past. Probably the cleanest rodents I’ve ever purchased. I swear they must live in a rodent resort. That said, expect prices to run accordingly and the shipping is high. Even so, it is still cheaper than buying live or f/t through any of the local shops...big box or mom and pop stores.
As to vacuum sealing, I sort and vacuum seal my rodents by serving size (rats) or in smaller batches (mice) to reduce freezer burn.