Dream Router & 3rd Party AP’s

Hello, first time posting to this community either here or back there if you know what I mean. I have just purchased a Dream Router to replace a TP Link Deco mesh system and would like to ask a couple of questions before I start tearing the old system down. One reason I got a mesh in the first place is because I have a building about 20m away from my house that I use as an office, I didn’t really want to run a wire from the house. The mesh just about gave me a connection and I could use the 2nd RJ45 port on the puck to get my ethernet only home automation system on the network down there. Speed is poor though and time moves on, my kids also use that space for gaming so a cable is now going to be run. My questions are these; can I use the old Deco pucks as access points to get me up and running quickly? They can be put into AP mode via their app. I also have two old DrayTek Vigor 2860n’s which can be put into AP mode, can I use them with UniFi without any problems? I was planning to run the cable directly from the DR to the office and then either connect it to an existing 8 port switch I have down there and plug a Deco puck into the same switch or just connect it to the DrayTek which would then act as an AP and provide 4 wired ports for use with various devices. Any advice is greatly appreciated!