it's so frustrating watching tiny incremental backups take forever over the network

While waiting for APFS to become stable, buy Carbon Copy Cloner. $40. I love it. It's fundamentally rsync, but tailored to OS X. For personal use a single license covers an entire household.

Every night CCC fires up on each laptop and each does an incremental clone to its own dedicated directory on my desktop machine. This clone is usually less than a few GB and takes about a minute to run. CCC doesn't have to be run daily, it can be told to run hourly instead.

Time Machine running on my desktop then copies everything off to yet another disk.

So my backup environment is:

   each laptop uses CCC to periodically clone to desktop

   the clones on the desktop are "traditional",
   CCC is told not to keep its own copies of modified files

   desktop runs time machine,
   makes hourly backups to a TM disk,
   old versions of files can be found there

This gives me 3 copies of all data on each laptop:

1) on the laptop

2) on the desktop

3) on the desktop's Time Machine Volume

If you create your users in the same order on each machine, or later go back and change the User IDs to match (under advanced options in Users and Groups) then the uids will match everywhere, and all files can be easily browsed in each location, with all file permissions intact.