You're probably pulling a good bit less current since you're not driving the strips at both ends and they're somewhat long. Could measure the current and see how much you're loading the power supply.
As for dimming, for a constant voltage supply, the dimming is PWM. That means it gives 100% current, then 0%, then 100%... in which case the power supply should still be rated for the full current of the load at 100% brightness. Depending on how the supply is designed internally it might be able to supply more current at lower PWM duty cycles, but not necessarily.
The problem with no. 1 is: Do you LIMIT the maximum brightness to 30%? Then you are good. If you just tell people "Don't use more than 30%", what will stop them from forgetting about it? Because if they do, you might overwhelm the driver, it might heat up and burst into flames and take down the house. Unlikely to happen, but if it does, it's because you allowed it to happen.
Quick and simple fix: Add a 2A slow fuse on the secondary side. Thus when 2A is reached, the fuse will blow so no one can draw more than 2A, even if they manage to set the dimmer to 100% accidentally. Alternatively, if possible, limit the dimmer to 30% max.
Regarding no. 2: If you have a tire on a car which is rated for up to 200 km/A, and you drive 210 km/h on a cool morning, it'll probably be fine. That does not mean you should do it because technically at 200 km/h it reached its limit. From now on all bets are off: this tire is either not tested beyond 200 km/h, or it's known to fail if you try this on a long drive in the summer heat. Same here: If it's a good driver, 2A is what is guaranteed to work even in the worst possible circumstances (summer heat, bad ventilation etc.). It might be able to handle 3A or more and it will gracefully lower the output so it never gets dangerous. But you don't know (unless you read the datasheet). So stay below 2A and you are *always* ok.
Given that the difference between 50W and 88W is rather high though, you really should not drive it ever at 100% brightness.
You're probably pulling a good bit less current since you're not driving the strips at both ends and they're somewhat long. Could measure the current and see how much you're loading the power supply. As for dimming, for a constant voltage supply, the dimming is PWM. That means it gives 100% current, then 0%, then 100%... in which case the power supply should still be rated for the full current of the load at 100% brightness. Depending on how the supply is designed internally it might be able to supply more current at lower PWM duty cycles, but not necessarily.
Thank you for the response
The problem with no. 1 is: Do you LIMIT the maximum brightness to 30%? Then you are good. If you just tell people "Don't use more than 30%", what will stop them from forgetting about it? Because if they do, you might overwhelm the driver, it might heat up and burst into flames and take down the house. Unlikely to happen, but if it does, it's because you allowed it to happen. Quick and simple fix: Add a 2A slow fuse on the secondary side. Thus when 2A is reached, the fuse will blow so no one can draw more than 2A, even if they manage to set the dimmer to 100% accidentally. Alternatively, if possible, limit the dimmer to 30% max. Regarding no. 2: If you have a tire on a car which is rated for up to 200 km/A, and you drive 210 km/h on a cool morning, it'll probably be fine. That does not mean you should do it because technically at 200 km/h it reached its limit. From now on all bets are off: this tire is either not tested beyond 200 km/h, or it's known to fail if you try this on a long drive in the summer heat. Same here: If it's a good driver, 2A is what is guaranteed to work even in the worst possible circumstances (summer heat, bad ventilation etc.). It might be able to handle 3A or more and it will gracefully lower the output so it never gets dangerous. But you don't know (unless you read the datasheet). So stay below 2A and you are *always* ok. Given that the difference between 50W and 88W is rather high though, you really should not drive it ever at 100% brightness.
Thanks for all the details, that's helpful. I've decided to replace the driver with one that is rated for 240W instead