What kind of Software are you using? If you need a screen capture software, download OBS Studio. If you need a video editor, download Davinci Resolve. Both are free and very good.

Regarding the watermark: I don't think anybody cares as long you can see most of the game clearly.

This question is not easy to answer. It is also the main reason why there is no glitchless category. For me glitches are tricks to break the (intended) rules of the game. For example: PseudoWaveBeam. Let's say a game rule is, that samus can't shoot through walls with standard beam. The devs implement checks to enforce this rule: All beams are collision checked with the the outside surfaces of world assets. If a collision is detected, the beam is stopped and the explosion animation is triggered. Speedruners now do slide jumps to force samus into a specific animation that always brings the weapon arm into a specific position, even then when it shouldn't be possible due to world boundaries. So samus weapon arm goes out of bounds. From inside the wall there is is no collision line that intersects with the beam-path, because collisions are only checked against beam-paths coming from the outside and not from the inside (due to math and performance improvement). So the in game sanity check that should have enforced the rule "no shooting through walls" was circumvented with tricks. Thats what I call glitch using. Some people argue that everything that the game lets you do, is allowed an therefore ok. Which is kind of the whole point of regular any% speedrunning. But nonetheless the conceptual general rule that "samus can't shoot through walls with standard beam" was violated. This is only my point of view. Others might see it differently. It is an almost philosophical question.

I can confirm PseudoWaveBeam and WaterBombJump still work in 1.0.2. It seems they only patched certain softlock situations and a bug with the IGT. Also It looks like they intentional avoid to touch any relevant gameplay glitches. I like it.

I also run glitchless. Also still quite casual. I understand that glitches are an important part of speedrunning. But I just don't enjoy using them. That beeing said, I don't think that yet another category should be added. The main problem is to define what a glitch is and what not. Who will review every 2 hour video and check it, update the rules as new glitches and techniques are beeing found? Someone might use WaterBombJump accidentaly. Should their run be disqualified? Even if no time was saved? I think it is just too vague for a solid category.

I currently register my glitchless runs under the "no major glitches" category. In the future I might use the "all bosses category" instead. But it doesn't really matter. I won't ever compete for a top ten ranking regardless of category anyway. So I'm just happy to beat my PB, share my runs and be a part of the community.