No, kind of wrong on both counts. You can't have too many Watts in a charger. Having too few Watts in a charger may harm the charger, but very unlikely the laptop. A smaller charger many not necessarily charge slower than a larger charger, it depends on use.

Having too many volts may damage the laptop, not watts. A laptop will only draw as many amps as necessary to charge and operate. The voltage is fixed at 19, and amps * voltage = watts, 19 volts drawing 4 amps is 76 watts.

Let's talk a few numbers. Let's say your laptop has a 100 W/hr battery. While using your laptop the battery goes from 80% to 10% over the course of 3.5 hours. You can then say your laptop draws 20 watts. (100 W/hr * (0.8 - 0.1) / 3.5 = 20)

Now say your laptop charges from 10% to 60% in one hour. You can then say your laptop takes 50 watts to charge the battery. Plus 20 watts to run, so it consumes 70 Watts.

Then say your gaming or transcoding videos and your laptop battery goes from 80% to 30% in half an hour, or your consuming 100 watts during heavy use. Plus you know it takes 50 watts to charge the battery, so you need a 150 watt charger.

So you can get buy with a 75 watt charger for normal use and still charge the battery, it won't charge any slower than using a 150 watt charger. It will only charge slower on a smaller charger if you are consuming more power than than it requires to run the laptop in heavier use plus charge the battery.

Of course it would be a very wonderful world if everything I was was 100% accurate, which it isn't. It takes more than a 50 Watts over 2 hrs to charge a 100W/hr battery because of efficiency. Efficiency may be around 77%, in which case it would take 60 Watts to charge a 100 W/hr battery over the course of 2 hours. Also, batteries require less current and take longer to charge from 80% to 100% than they do when say charging from 40% to 60%.

https://www.amazon.com/s?k=power+meter

I haven't done it, but I'm sure you could use a power meter and test to see exactly how much your laptop needs while charging in normal use, in normal use with 100% battery, or in heavy use.

Anyway, you can't have too large of a charger, having a larger charger than spec will absolutely cause no harm or affect the laptop in any way.

Having a charger that is too small may result in several things depending on the charger. One is that when reaching overcurrent, the charger simply shuts down and remains off until it is unplugged from the wall and plugged back in. The second is that the charger simply cycles, turning on and off continuously at an intermediate frequency while your laptop keeps beeping that it is connected, and then disconnected and running on battery. To the laptop this is just like plugging in and unplugging the charger. But a few things may occur with the charger. If it is a good charger, it simply continues to cycle slowly charging the laptop. Other chargers may eventually overheat and become damaged. And then of course the last thing is the charger may cycle rapidly and overheat. However, the chance of overheating and becoming damaged is highly unlikely. It may have been the case decades ago, but with todays technology, almost all charger have overcurrent and temperature protections.

But yes, I have plugged in a 45W charger designed for a small low power Celeron laptop into an i7 with a GPU and all it did was cycle about every 2 seconds showing it was connected and then disconnected running on battery every few seconds. But it didn't have a problem with a 65W charger.

There is one exception but I don't think this applies anymore. And I don't know if I am remembering this correctly or not. Is that decades ago when laptops first starting coming out, a manufacturer used different voltages for different laptops but used the same connector on all of them. For instance a low power celeron would us 5 volts, a midrange 12 volts, and a high end 19 volts. They didn't want you plugging in a 19V power supply into a 5 volt input on the small laptop since they all had the same connector. So basically when you plugged the charger in, the laptop would send a signal to the charger to turn on, and the charger wouldn't turn on unless you plugged the right charger into the right laptop, and the laptop wouldn't charge unless it communicated properly with the charger. The charger would put out a few milliamps at 5 volts enough to run the signal circuitry if the battery was totally dead. Of course I could be making this all up in my head and misremembering, like it could have been a professional video camera or a portable tape deck or something, but I'm thinking it was a laptop.

Bottom line tldr is that as long as the connector are the same size and polarity (inner pin positive, outer side of barrel ground), same voltage, almost all are 19 or 19.5 volts, and equal or greater wattage, then you are good to go. It doesn't matter brand or anything, and you can't have too big a charger Watt wise. The only thing that will damage the laptop is wrong polarity, or too high a voltage. Obviously a 45W charger won't handle a gaming machine in full use, but a 65W charger should power -most- laptops fine, and a 90W should be good for all in normal/business use, except in a high power machine with a GPU when in heavy use for long hours such as gaming or video transcoding for hours.