OK, so 'bouncing' just means you record material on one track and then transfer it to another. It implies patching the output of the one channel to the input of the other on the deck so, if you need to transfer more than one track at a time (which you will do, otherwise you don't gain anything), you need a mixer as VinylDavid pointed out. For example, if you recorded tracks 1, 2 and 3 and wanted to then put all three of those onto track 4, you couldn't patch the three outputs to the one input without a mixer. Well, theoretically you could use some sort of 3 to 1 adapter but you'd have no control over the levels and it would sound like crap.
So, to record 7 tracks without going beyond 2nd generation (bearing in mind that my definition of '2nd generation' is first copy -- after copying for the first time, the tracks have now been recorded twice, same as if you copied them to another tape):
- Record on tracks 1, 2 and 3.
- Bounce tracks 1, 2 and 3 onto track 4. Now all three recordings are on track 4 and tracks 1, 2 and 3 are free again.
- Record on tracks 1 and 2.
- Bounce tracks 1 and 2 onto track 3. Now both new recordings are on track 3 and tracks 1 and 2 are free again.
- Record on track 1.
- Record on track 2.
So, that gave you three recordings on track 4, two recordings on track 3 and one each on tracks 2 and 1, giving you seven recordings on four tracks with none going beyond 2nd generation. Note that I have started using the word "recording". The three recordings on track 4 are now one track. Their levels are fixed in relation to each other (as decided by you at the mixer when you bounced them) and they can no longer be manipulated individually. This is one reason why more actual tracks are better (others being noise accumulation and time/effort involved) because, the more tracks you have, the more recordings ("parts" if you like) you can keep separate and control individually. So, in other words, you have to plan in advance if you're working with less tracks, otherwise it'll be all wrong when it comes to the final mix-down. The mix-down is when you take all the material you have accumulated on the multi-track and transfer it all down to two stereo tracks -- typically on a separate, 2-track machine. Obviously these days there are 5.1 mix-downs and various other formats too (and back in the day some people did Quad mix-downs) but you get the drift.
Now, if you wanted to go beyond 2nd generation, here's how I can see the way up to 11 tracks:
- Record on tracks 1, 2 and 3.
- Bounce tracks 1, 2 and 3 onto track 4. Now all three recordings are on track 4 and tracks 1, 2 and 3 are free again.
- Record on tracks 1 and 2.
- Bounce tracks 1 and 2 onto track 3. Now both new recordings are on track 3 and tracks 1 and 2 are free again.
- Record on track 2. You now have six recordings stored.
- Bounce tracks 2, 3 and 4 onto track 1. Now the previous six recordings are on track 1 (with most gone to 3rd generation) and tracks 2, 3 and 4 are free again.
- Record on tracks 2 and 3.
- Bounce tracks 2 and 3 onto track 4. Now both new recordings are on track 4 and tracks 2 and 3 are free again.
- Record on track 3.
- Bounce tracks 3 and 4 onto track 2. Now the two previous recordings from track 4 are on track 2 (at 3rd generation), mixed in with the previous recording from track 3 and tracks 3 and 4 are free again.
- Record on track 3.
- Record on track 4.
So, that gave you six recordings on track 1, three recordings on track 2 and one each on tracks 3 and 4, giving you eleven recordings on four tracks with none going beyond 3rd generation. I used an over-and-back approach above with the track numbers just because I think it makes it clearer (probably not) but the order you use the tracks in doesn't matter.
As I said in my earlier post, it might depend on the definition of 'generation' (is '2nd geration' the second copy or the first copy?) and I can only see the way to 7 tracks without going beyond 2nd generation so I'd love to know how to achieve 10, if it is possible. But, using the other interpretation of 'generation', I think that makes it 11.
In any case, just as though you were copying a cassette to another, every time you copy over, the background noise accumulates. Thankfully the background noise is very low on R2R at 7.5 or 15 ips but there's still a limitation as to how far you can go. That AN-300 is a Dolby-B unit. Dolby-B has never done anything for me but that unit is a much more professional unit than the simple button you find on a cassette deck, i.e. everything can be tweaked and calibrated on it. If I were you, I wouldn't worry about that right now and see how you get on without any NR. AN-300s are hard to come by in any case and most are likely to be gone out of whack by now. Come back to the NR discussion if and when you feel the need as there are other options like DBX and even software to consider.
Regarding "Would acquiring more Reel To Reel decks be beneficial?" Well, I'll leave it up to you to discover how much benefit you'd get from having more but, if you're like me, once you get one of them, you'll want more whether you need them or not!