Daily lineup changes is very common. All that means is that you can update your roster daily, as opposed to weekly or some other interval. It sounds more complicated than it is.
200 games started may or may not affect your draft depending on how deep the league is. If you figure the average healthy starting pitcher has about 33 starts in a season, then 200 games started would allow for approximately 6 full starting pitcher seasons. Therefore, if the league is fairly shallow and one could easily draft more than 6 roster-worthy SP's, it's definitely worth considering the games started limit. For instance, if you know you can still get a quality starter for your 4th/5th/6th SP spots in later rounds, your earlier picks might be more wisely spent on hitters or closers. And during the course of the season, keep the 6 SP rule in mind. If you have a rotation of 7 or 8 SP's going at one time, realize that at some point you will have to cut back to 4 or 5 to balance things out, or hit your GS max early. You best bet is to try to develop a core group of 6 reliable, quality SP's and stick with them. If you find over the course of the season that quality SP's are readily available on free agency, you can try to sell some of your pitchers that might have more recognizable names but stats not far off from the free agent guys to less savvy managers in exchange for a big bat or a closer or something. Depending on the experience of your fellow managers, you might not have much success, but it's worth a shot, and there's usually at least one sucker in every league. That said, the elite SP's - 15+ win, 180+ K, sub-3.80 ERA type guys - are probably worth MORE in a league like this because they'll give you the most bang for your buck (read: stats for your starts, which are limited). If I were you, I would draft 2 or 3 of the elite starting pitchers early on and pick up the rest much later in the draft. You'd be surprised how many new pitchers emerge every season that equal or surpass the typical SP taken in the mid-late rounds of the draft.
Sorry if that's too much information at once, but to sum things up and directly address your original question, daily lineup changes are very common and nothing to worry about, and unless you're playing in a deep league, a 200 GS limit probably does diminish the overall value of starting pitchers a bit, but gives a slight boost to the value of elite starters.