Home studio reel-to-reel recorders generally use quarter-inch audiotape and two or four tracks. Two-track recording means half of that quarter-inch is used for the left channel and the other is used for the right. Four track has two meanings. It could have two tracks going in one direction, then flips the tape over for two more tracks going the other direction. This doubles the length of recording time but decreases the overall quality. The other meaning of four track is four parallel tracks that each can be recorded separately for sound-on-sound multitrack recording. If you intend to record all the parts of the music and vocals yourself, this is the type of machine you need. You also need fast tape speed for cleaner recording and less hiss. Ideally, this would be 15 inches per second, but 7.5 inches per second can be used.
Analog tape is more forgiving than digital. In digital recording, if you go above a certain recording level, you hit the digital "brick wall" that clips the sound, makes a cracking noise and blanks the music. This generally renders a recording useless. Analog tape will distort slightly if you go beyond the specified range, but you still get music recorded. Still, keep an eye on the VU (volume unit) meters for each track to avoid over-distorting the recording. Analog tape does have tape hiss, but later open-reel machines had dampers for this, including Dolby noise reduction.
To record multitrack music---you playing or singing more than one part---you can use the built-in sound-on-sound of some machines, but it can be problematic, especially in lower-end recorders. The safest way to record in multitrack is the same basic technique the originator of the idea, Les Paul, did it. He used two recorders and went back and forth between them. Record the basic guitar part on one reel-to-reel recorder. Wire that recorder into a second open-reel recorder and attach headphones. Put the headphones on, plug the bass guitar into the second recorder, start the second recorder, then start the first recorder. The music from the first will go both into your ears and into the second recorder. You then can record the bass line onto the second recorder over the top of the original recording, mixing them.