Almost any FS/CFS AP is going to have the basic altitude and level hold features. The key is using an AP that also has heading hold. When this is activated, the plane will automatically begin to steer to the default heading of 360 prescribed into the defair.flt and defgrnd.flt files of the SITUATIO folder. But when you use this in conjunction with the common, mouse-able CFS2 magnetic compass installed on the panels of all flyable stock a/c, you can use the magcomp to correct the heading like a steering wheel. It automatically connects with your active AP gauge and takes over the heading function.
So, with these two, you can go hands free and just steer the plane with mouse clicks on the magcomp. This is how you manage a bomb run in a medium and heavy bomber as bombardier. Its basically the same method used by the guys peering into the Norden sight. They steered to their aimpoints in AP mode with nothing more than a few knobs on the sight. Even better, using any of the two gauges i've posted above, you can even bypass the magcomp altogether. All of the incremental features on these two mouseable gauges can be adjusted on the fly. For example, if you activate heading hold, you can click on the heading number to the left or right to adjust. Same with altitude and vertical speed.