Shared storage solution Windows n Mac

Question

Good day,

while not precisely a server storage question - that was the tag that matched most closely.

I need to regularly back up files from 2 computers at our church - one which records service audio - one which records audio/video.

Originally both PCs were windows and I had intended to place external drives on each then have each PC back up to the local and remote external drives for a cheap redundant solution.

However when the video PC crashed, they replaced it with a mac and blew all of my plans out of the water.

I am now looking for a single solution that will support both PCs.

Im looking for about 8TB total space.

Speed isnt critical since these would be off-hours backups.

Im not well versed on Macs and right now Im thinking my best or only option would be a small NAS - like a mirrored Synology.

Because we're trying to keep costs down, and adding a NAS will increase the original cost estimates by hundreds of dollars. I wanted to reach out and see if anyone had any suggestions - or if the consensus was that a NAS is the best approach at this point...

thanks for your input.