Speed Doubler is primarily important if you use
System 7 on PPC Macs, where what it does mainly is replace the 68k emulation bits that are built into the OS with some more efficient ones. You might not see a difference if you only use native PowerPC apps, and you install all of the other
recommended updates, some of which are newer than 7.6.1 itself is, and should be better optimized for PPC.
For my part, I haven't put Speed Doubler on my 1400 yet and it's "fine" (Although: I have a /166, it would make a much bigger difference on the /117) but I should eventually, since there's a few 68k apps I do use on the system.
If you're using Mac OS 8 or newer, you shouldn't strictly need either, although some of the memory management tools might be important, especially if you don't end up getting your hands on a 64 meg RAM upgrade.
One thing that might be worth looking at (which I haven't used before) is
RAM Charger, which alleges to manage RAM more efficiently. I haven't used it, but over a few years LEM did a few different articles where they say that it works really well - could be worth trying out.
Also worth noting: At the very least, you should leave the built in virtual memory enabled. Without it, applications will likely end up using more RAM and launching slower.