I play STW and MTW/VI. I've only played STW online.

As far as unit type for a general goes, I prefer a cavalry unit for it's mobility. The little moral bonus that a general provides when he's nearby is useful, and having my general mobile allows me to use that bonus more effectively. In STW MP I have often used a souped up Yari Samurai (spear) unit as a general with good results. There are a lot of MP players that handle cavalry well, and they often like to try and flank you and try to kill your gen. It's much harder (but not impossible) to do this if your gen is a spear unit in STW. I usually use a ysam in battles where my army is likely to stayed grouped relatively tight, and where high mobility and sustained movement is not likely to be an issue (defense for example). An except is where I use the "4444" army, which I describe below.

As far as MP army composition goes, I tend to go with 2/3s of my army balanced, but with slightly more cavalry than is usual. I am aggressive even in defense, and use cav to bait and harrass my opponent's flanks while pressing the center with my main army. This is a common tactic, but having more cav allows me to worry those who bring more "normal" numbers of cav--two attack and two cav archer units being common.

A highly successful 10K army that I used for a while, and that for a brief period was copied by quite a few players on STW last year, was what I ended up calling the "4444" army, which consisted of a ysam gen and 3 additional ysams (h7w1 or h7a1), 4 Cav archers (h0), 4 musketeers (h2), and either 4 Nag Cav (2-h4 and 2-h3 if my ysams were h7a1), or 2 Nag Cav (h4) and 2 Heavy Cav (h3) if my ysams were h7w1. Despite the low number of infantry units, if the cav were used to good effect the army really kicked butt. Some purists complained that using ysams with such high honor and upgrades was exploiting the stat imbalance, as they could beat the typical MP no dachi and and monks unless they were significantly outnumbered and flanked (which they often were if my cav didn't do their jobs effectively). My argument was that their high cost forced me to sacrifice with the rest of my army, and I pretty much had to use my Cav Archers (very flighty at h0) to good effect and keep on the flanks and rear of enemy units, or I'd get wiped pretty quick.

When playing campaigns in MTW I use balanced armies. I don't use a lot of cav in MTW, usually 4 units max. If I'm playing the Egyptians or Turks I use a couple more, as they have good cav archers (the Egyptian Mamluks in particular). The Spanish are also an exception, as I love Jinettes and use them to great effect. I've only played the Hungarians once or twice, but their Skelezy are great so I use a few more cav with them also.

STW campaigns depend on the faction, but I do love a LOT of cav. Playing Takeda is hella fun, though I find it to be really easy against the AI, even on Expert difficulty. Surrounding the enemy to get the Yari units chasing my cav, pulling them away from their archers, and then sending in reserve cav to decimate the ranged units while the Yari are away is a favorite tactic and usually results in a rout. Then I can mow them down as they flee, with casualty ratios usually being 8:1 in my favor or better. Cav archers in STW campaigns are very cool. In campaigns they have higher honor that you can normally afford in MP without having to make cost-ineffective sacrifices, so you can use them to melee attack flanks and rear of ranged units and enemy cav archers without them routing (if you time it right and pull them out as the charge effect lessens). If your timing is good you can often cause a mass rout doing this in several places at once.

So in summary, Cav general usually, highly mobile and aggressive style, bait, draw, attack ranged with cav when the opportunity presents itself, pepper infantry with highly mobile cav archers until everyone's running, then mow the lawn. But being unpredictable doth a good general make, so I don't always play like this--just more often than not.