Does snaps slow down the boot?

You can probably get more detail about what's consuming resources during bootup using the systemd-analyze command. For example:-

systemd-analyze blame

This will list in order of time used, each thing that consumed time during boot.

systemd-analyze plot > plot.svg

This will generate an svg called "plot.svg" which you can open using an image viewer app. It shows graphically what's eating up your machine during boot.

Someone already Explain it.

Using Snaps for having up-to-date software, we end up paying for it with higher network traffic, more disk usage and slower boot time. If you do not want to use Snaps at all, then remove them with sudo apt-get purge snapd.

See more here Details about Snap Mount