Definitely seeing some people complain about the design changes
The great thing about Mastodon is, that you can freely chose what client you use. If you dislike the original client or web interface, just use Elk, Semaphore, Tusky, etc. whatever you prefer.
Absolutely. SSDs, systemd, and recent kernels definitely help. From the moment the EFI hands over to the kernel, my ca. 9 years old system is ready for login 3 seconds later.