I'm not sure that you can easily install anything on a Synology NAS, they are pretty locked down and would require a lot of tinkering to even install Hexos. So I would not go down that route.
Also make sure that you get something with a video output, or else installation and management in case you locked yourself out will be a nightmare. Also it is not possible to use the boot drive in a Pool, meaning if you have a 3 storage bays, 1 drive will be used as a boot driving, leaving you with only 2 drives left. Take this into consideration, that you also need space for a dedicated boot drive.