"1 (2) seeds" means that you are connected to 1 out of 2 available seeds. Thus, "1 (4) peers" means you are connected to 1 out of 4 available peers.
There really isn't any "optimal" ratio of seeds/peers. You could max out your download bandwidth from one single seed, regardless of how many peers or leechers there are. In general, the more seeds, the better, as this gives you more places to connect to to download the file. So, yes, a torrent with 100 seeds may be slower than a torrent with 1000 seeds. It really depends on the upload speed of the seeds themselves.
A number of reasons could prevent you from connecting to all available seeds. Note that the numbers in parenthesis are the total number of seeds and peers as reported by the tracker, which may not be correct. Some of these seeds may not have their torrent clients open at the moment, or may have reached their maximum amount of connections, so that they are not able to connect to you.