I try to hit some points for you
If it says 50-200rms then 200 should be the max and it should work ok on 50 up to 200 amp. Ratings other than RMS are really b* and usually just double RMS, though some amps do not double RMS for peak output. If a sub says 200RMS that should be 200RMS max, should not use over a 200wrms amp....however a larger amp can play cleaner and maybe have more control depending on quality of it, so that is why it can be better to use a larger amp (often done in SQ setups). Then again, if you max out the larger amp likely it will blow the sub at some point but it really depends on use. If you play it really loud it can blow, if you play bass tracks that max out the sub system it will put more stress on it. If you play loud for extended time it will get the VC hotter and may eventually blow it when you are exceeding or on edge of ratings. Note that clipping any amp might cause something like double the RMS to be put into the sub as explained on Perry's site.
The enclosure has a lot to do with what sub will handle. A sealed box supports the cone more so it does not hit xmax so you can usually run max rated power, or thermal rating (the rating you see on it). If you use a ported box sub it will get out of control below port frequency, you need a subsonic if you lay the power to it. IB install (free air) has no support from a box, so often you figure half the rated wattage as max...your 200wrms sub will take 100wrms before it hits xmax and runs out of physical travel. That is guess, you would have to inspect them in use to know exactly. A large ported box might hit physical max before thermal also.
Another issue is efficiency, the SPL db. Often a higher power sub has a lower efficiency because the cone/VC wire/etc is bigger and does not work as well. Think of a light econo car and a heavy truck. Truck takes more power/gas to go 60mph and gets there a little slower....but it can haul a big load that would crush the car. What happens is if you take a 100w amp (econo car size motor) and put it on a 1,000w sub (loaded truck) it does not go very loud (can't get to 60mph). If you put a 100w sub (econo car body) that is more efficient on it, it will go loud but may blow up if you clip it or really beat on it. Note that more expensive subs might be more efficient and still take a lot of power. This efficiency is why it is generally better to match your power up sub to amp depending on how you will use/care for it instead of getting a sub with way more power handling than you need. Unless you plan on a larger amp soon of course.
One last gray area is the ratings themselves. Subs might be rated above or below what they actually can take in a variety of situations...and amps are as well. Depending on brand and so on, it is not a precise thing even if they are good ratings because of all the variables just in musical signals themselves...how they are mastered...even instruments used. You can get a great idea with a sine wave, but that is not music. Then toss in the enclosure and it is a pretty murky area. But the ratings are supposed to give you an idea and they do.
If you don't see RMS on the rating, it is usually MAX that is double or more than real RMS. With amps they even rate RMS at 14.4v or at 1khz so it is not even a true rating then as you often will never see constant 14.4v in a car and is usually easier for an amp to make 1khz tone than 20hz-20,000hz entire span of human hearing as is the real standard. But if two amps are rated the same way then you should be able to compare them. With subs they may take a peak of much more than RMS before the VC heats up enough to melt. Thus 300wrms and 1200w peak. Amps often don't make over double RMS for peak due to electronic reasons. Either way peak is not listening to music so it's still really only a marketing ploy to put a larger watts number on the box.
That kind of sub can work well for the IB setup with lots (4 12s) of drivers I run. Subs often have higher quality sound at lower travel and you can't put big power into IB subs anyway. Right now it shakes the car at 100wrms each...don't really need much more power for my use so I may as well try more efficient/cheaper/lower wattage/and lighter weight subs right? These infinity work good but are heavy when x4 in my little car. I could hardly manage the baffle loaded, and I'm not a little guy. I certainly could not get it set right in the trunk on my own and screw it in at same time. A big heavy box, that was what I was trying to get away from.