Proportions definitely changes the theme of the game. If you are interested in a Proportions-type mod, but want strong AIs, check out AI Campaign. It is based on Proportions, but is modified heavily to make up for a lot of AI short-comings.
TDM only alters the AI, leaving all of the stock techs, comps, etc. intact. It is a must-have.
Devnull is also a mod that gives more challenge from the AI, as there are a number of new components that it can use better, and its AIs are modded rather well. It is not too different from stock SE4, just with some neat new toys added in.
About my PBW games... confidence that the orders you issued Last turn are good and don't need to be second-guessed certainly cuts down on micro-management a lot. So does using repeat orders, the "Fill Queue" option for build queues, etc.
In Gold, you can select multiple build queues at once and order the construction of ships and/or units at multiple SYs at once. You can, for example, select 100 planets and tell them all to build the Ravager class BB. This greatly cuts down on the MM, and for this reason alone, I hate playing pre-Gold SE4.
Gold has a lot of changes (especially in the patches) that help the AI out, but it does not change the AI into a super-powerful force. You will still need TDM, Devnull and/or AIC for that.