The RAM limit is a pain on early LCs. If you add two 4MB SIMMs to an LCII, you should have 12MB (4MB onboard), but will only be able to use 10MB of that. Unlike the 32-bit dirty Macs, which could only see 8MB without special software, there's no Mode32 equivalent to let you use that RAM.
I recommend just leaving the 2MB onboard on your LC and getting a pair of 4MB SIMMs to populate the RAM slots. The 512K VRAM upgrade is also worth it if you're going to be using anything 640 x 480 or larger and want 8-bit color. (With the stock 256K, the only monitor capable of displaying 8-bit color is the 512 x 384 12" RGB, which was often sold alongside LCs and LCIIs and is contoured to match the case perfectly).
The LC II, by the way, uses what is essentially a modified LC I board. The key differences between the internals of the LC and LC II are:
-68030 in LC II vs. 68020 in LC; both run at 16MHz and have a gimped data bus, limiting their speed (the LCs have a 16-bit data bus; the II and IIx had a 32-bit data bus, which allows them to run faster despite identical clock speeds)
-4MB soldered onboard the LC II vs. 2MB on the LC
-No second floppy connector/case slot on the LC II
-Different fan and speaker assembly (interchangeable with later LCs, making a logic board swap to an LC III/III+/475 easy)
-Presumably both have identical minimum system versions, although I've never tested or read about 6.0.6 on the LC II (6.0.7, contrary to popular belief, does run on an LC II--I run it on mine)