String is one of the most important part of every racket. They’re something which can entirely change the racket’s performance. A good string appropriately setup should give you good resilience, good feel, less shock, more control. Of course, you also want it to be durable. So you don't have to restring frequently.
You cannot match any string to a particular racket. What you can do is match the string and its tension to what you need. I emphasize the word NEED as there’s a major difference in what you NEED and what you feel would be good for you.
Now for any recreational/club or even a district/state level player I would recommend using the Yonex BG65 strung in the 23 lb to 25 lb range with a gap of 2 lbs between the cross and the main string beds (the cross bed is strung tighter - e.g. 22 lb - Main, 24 lb - Cross). If you’re playing with a plastic shuttle then there is absolutely no need to go beyond 24 lb in the string tension and practically no need to use any other string than the Yonex BG65 .
However, if you’re playing with a feather shuttle then the strings do matter much more as accuracy comes into play a lot. Feather shuttles require more accuracy than power to hit winning shots. Now, if you’re using feather I think you would be probably above the basic club level and are looking play competitively.
So the basic principle for badminton racket stringing for competitive play/practice for competitions is this:
HIGHER TENSION (26 lb +) = LESS POWER & MORE ACCURACY
LOWER TENSION (Up to 24 lb) = HIGH POWER & LESS ACCURACY
Higher tension results in the shuttle staying on the racket strings for a shorter time which results in lesser power as the rebound effect is reduced. However there is a rise in accuracy. Higher tension also means that the strings can break faster and if you go beyond 27 lb then even the racket is at risk. At the national/international level we use tensions from 28 lb to 31 lb. This is why our strings break almost every two days and rackets break frequently too! But that’s a headache for the companies sponsoring us ;) We use such high tensions as we do not require any power from the strings as we are capable of generating enough power ourselves. Accuracy is our primary concern. But it takes a long time to reach that level……
Yonex BG65 - A combo of durability and even performance, it’s the most cost-effective string and is the top choice for any unsponsored and/or recreational player and has a soft feel.
Li-Ning AP 75 Turbo Badminton Racket String - An offensive string which offers good smashes and high repulsion. A string commonly used by attacking players. Has a hard feel.
Yonex BG66 Ultimax - Another high repulsion string which offers superb accuracy and power. However it’s one of the least durable strings and if you’re using it in your rackets be sure to carry at least 4 rackets for the match. Has a medium feel.
Yonex NBG99 - A control-based string with a rough texture and decent durability. It’s good for defensive and placement-based players. Has a medium feel.
Li-Ning Badminton Racket String No 7 The thinnest and most repulsive string which offers great accuracy and the highest power. I use this string in all my rackets and I’m in love with it. The biggest issue in it is that it has abysmal durability owing to its 0.61mm thickness which is just too thin to be durable. It hardly lasts a day or two in practice and breaks approximately 3 times a match :( Has a medium feel.
Yonex Aerobite - A hybrid string in which the cross string is of 0.61mm thickness and the main string is of 0.67mm thickness. It offers a very unique feel and it does give great control. However it differs from player to player and I’ve found many players who are unsatisfied with it while others worship it.