

The maximum internet speed you get is the speed of the slowest link in between your house, your ISP, any other network in the middle, and the ISP you are using to connect your remote device to the internet itself
On top of that, put tailscale. Assuming packets go directly between home and your remote device, then tailscale should not impact. But if the packets do go trough a tailscale server, like you have no public IP address at home, or CG-NAT, then that will be the bottleneck most probably.
Tailscale on itself isn’t a measurable overhead.
In general, for home network speed, consider your home UPLOAD speed (as that will the seen as “download” speed from outside) not the download speed, which is often many times faster.













No, really, wireguard encryption overhead is negligible unless you have a really old CPU (like a Pentium100 or something).
Whatever slows down your N100 is not wireguard per se, probably some tailscale overhead going trough their servers.
I have a fairly dated rented server, with an Atom D510, 2 cores, which is 10 years old, and accessing it over wireguard or not, I can still max out the network bandwidth without any visible CPU overhead.