About a return pump, the DC pumps are nice but I question their reliability long term with head pressure. My experience with basement sumps has been with pressure rated magnetic drive pumps such as iwaki and now Panworld. They are designed specifically for pushing up water at distance they are rated for. Their track record in the hobby for these applications are well known, some lasting 10+ plus with little maintenance. DC pumps, well I've always stuck to what I know works.
As far as redundancy, having two return pumps is ideal. One in service and one as a backup is the way to go. I have a Panworld 100Px as a backup just in case, but it probably won't ever be needed as a temporary return pump as the 150 is a beast like it's iwaki counterpart. It's been running now for over 5 years now with, as expected, no issues. That's what you want, a return pump that you don't worry about.