LA Rlyeh is one of my favorite factions and probably the one I spent the most time on trying to figure out a game plan for.
Summod greatly improves the faction because it makes all your free spawn insane guys upkeep free which is the real disability to the faction. Other wise you're going to have to manually move all your Insane Tritons into areas where there isnt many supplies so they get diseased and die off.
Other wise I do what you do and take the Void Lord, though I ignore major blesses. (If you were to take one I'd go with N9 because void spawn tend to have enormous bulk) I usually only go for 9 candles, but that's just my preference since you'll be building so many temples anyway Dom 10 is easy to get.
I usually do something like D5 to enhance the void lords natural fear, E5 for extra prot and good buffs, and then the rest in Astral so I don't get Dueled to death later on, other wise the Void Lord makes for a pretty good single expander even without a shield.
it's a good idea to forge an affliction blocking charm for him early on in year 2 because you'll still be expanding
The game plan for LA Rlyeh follows much the same as EA Rlyeh but with easier execution. First off know who your opponents are.
LA Atlantis is designed to kill you if you don't focus fire on them right away, and they'll always start on a coast.
LA Xibalba is easier to deal with, LA Lemuria can be a pain in the ass if you don't keep them out of the ocean, and expect your insane armies to be nearly useless against them. but your troops have high MR so it balances out
The only way you can win is by turtling the entire time, You'll want to get Burden of Time going since your guys and star spawn have life times in the thousands. Basically you want to monopolize the global slots over everyone else because you're going to be a sitting duck most of the time.
Armageddon (wish) is your game ender, when you've totally exhausted any other possible enemy you can then more safely capture provinces.
Now those are your beginning and ending big moves, to fill everything in between getting Evo 6 for Mind hunt is essential, whispers of Rlyeh is shit for remote assasinations, and you're better of using your death gems for behemoths or something undead to help your Star Spawn kill more inbetween your insane armies.
The next thing I'll mention is your unique summon which causes insanity, not only does it do that, it also comes with Astral 4 which means it can do some decent pentrating soul slays.
another good thing to look at is your assasins's they're probably the best spell casting assasin in the game. Just give it a water bottle and watch it go to town with mind blasts.
Another note; your insane units are "mindless" so you dont need to worry about feeding them so much, but it helps them rush into place faster if they're not at risk of becoming "limp" from disease and starvation.
I think that pretty much covers it.