Boot time is "controlled" by the speed at which the installed programs and services can load. So to speed it up:
- Have a faster boot disk (using a faster SSD or similar - faster storage to load the programs from). You have this, so....
- Probably DON'T need to worry about faster memory, though more of it and using
preload could help with some programs particularly after boot. 6GB should be enough for now!
- Removes unnecessary services (or dont install them in the first place)
The latter is the cheapest, and you already found one of the more ideal solutions in systemd-analyze (for newer linux systems). The blame option lists the services that take longest to complete (note, ones like plymouth, have to wait for other services to finish starting to complete, so removing them wont improve boot time by much).
Some services are important to the systems operation, so aren't ideal to remove (e.g. NetworkManager), but perhaps can be configured so no errors occur or it doesnt try and load stuff you may not use (e.g. lvm). If you post the top output of blame in your question we may be able to help with this!
Also, running systemd-analyze plot > file.svg will give you a visual overview of the boot time (as an image file.svg). Other methods are listed here (but surprisingly misses the plot option covered here).
The options you added are explained here. I'm not sure if I've heard of uses for them outside of dealing with weird video hardware, but any speed increase here is from skipping the splash screen. It might increase speed a bit but the output shows its starting up properly (i.e. I wouldn't bother except on a computer without a display in a fixed state).
