What does the axe gauge do with the switch axe?
Switch Axe has 2 gauges, all on the same little graphic of the switch axe below your stamina bar. The little line on the inside is your Sword Mode gauge. It goes down as you use sword mode attacks. When that meter gets below the cutoff on the icon, you can no longer use sword mode until you "reload" it. This is done a variety of ways in this game, like using your unsheathed wirebug ZL + A move, or just hitting ZR when it's below the cutoff. You generally want to avoid that in combat though, because it locks you into an animation that's long and you can't cancel out of.
The "outline" of the graphic is the 2nd gauge, it builds up as you use sword mode and connect with hits to the monster. Once that bar is full, both your sword and axe mode hits deal additional damage (related to the phial type of the switch axe) until it runs out. I think it's default 40 seconds or so, but can be extended with skills. Also, when it's full and blinking, you can do the mounted discharge move. Essentially, if you hit a monster with the X+A sword attack anywhere while the gauge is full, it will mount them, you jam your sword in its nearest mountable part, and then mash X to do a shitload of damage and finish it with a huge explosion. Unlike in World, you can actually stay on even if the monster does an attack or two, but you will still take damage if it's an attack that would use the body part you're mounted to. There are also bigger attacks that will throw you off, but it's a lot less likely than in World.
There's some sort of hidden stat in this game that affects how quickly the second gauge builds up, and I haven't figured it out yet. The Nargacuga SA for instance will fill up in about 5-6 hits, but the Magnamalo switch axe will take a good 15-16 hits to fill it. At first I thought it might be affinity related, but I think it actually might just be a hidden stat for each Switch Axe, which is frustrating. At any rate, hope this helps.
Anyways, I just went through tonight and cleaned up all of my 1-2* hub quests that I skipped, trying out different weapons every 5 or so hunts. I tried SnS, Gunlance, IG, and Charge Blade. I unlocked at least 2 of the switch skills for each of them, so I played around with the various uses of each. Afterwards, I pretty much decided that SA and IG are the only two weapons for me in this iteration.
Gunlance is more mobile than it used to be, but I just can't get a feel for when I should be shelling vs. poking, and I hate the feeling of waiting for the monster to come to me. Maybe it'll get easier on higher ranks where the monsters aren't so passive. It also has so much going on, I never know which move or which attack to use at any given time. I'd say the complexity is right up there with Charge Blade this time, with all the switch skills taken in to consideration. That aerial full burst is god damn satisfying though.
SnS is very busy, but until I get a Flinch-Free deco I'm going to put it on hold. 90% of random co-op that I do is with Longsword users and you can imagine how that goes trying to do literally anything. So frustrating. I can't imagine why with all of the QoL improvements they made, that they still kept friendly tripping in, especially after making Longsword (an already popular weapon) really strong and a weeb magnet with the new moves.
Charge Blade kinda sucks for me in that the whole weapon is just one big boring pattern of building up phials and charging stuff just to do SAEDs. The aerial SAED switch skill is so satisfying to do and much easier to aim than the ground version, but I still get really bored of the gameplay loop which has no real room for playing differently. At least in Iceborne they had the spinning axe mode that you could leave the weapon in to hit tails or larger enemies. As far as I can tell, that's been removed in Rise, but you can do 1 hit of spinning axe from a switch skill. It's a shame that they didn't make sword and shield mode more viable instead of just a "reload" for the big damage.
Insect Glaive at a glance didn't seem to get the love that the other weapons got, but people are skipping the fact that they totally redesigned the kinsect functionality. Whether I like it or not, I can't say yet. In World, the bugs did everything, so you could build a fast bug with blast dust and never have to look at them again. Now there's all sorts of considerations to make. You have the bugs that attack on their own and leave powder, but they're really slow and their per hit damage is low. Then you have super high damage bugs that travel mid speed that leave no dust. Then you have fast bugs that pull 2 different color extracts each time they hit. I have generally just been using the powder bugs for now, but for faster enemies I think that dual extract one will be awesome. The wirebug moves aren't great so far, one launcher that almost always overshoots the monster you're trying to hit, and one tactical retreat that also recalls your bug. Kinda boring, but I know I saw another one in videos that shoots straight down and does a diving attack for big damage. I haven't unlocked that one yet though. Anyways, I've been having fun with this weapon, the new Tetra slash switch skill gives it a little needed oomph for ground combos, and the spinning approaching switch skill is just flat out amazing. Lots of fast hits for decent damage, and has a built in counter that initiates a jump if you're hit while you're spinning towards the monster, which you can then do aerial attacks with.
Anyways, yep, love this game. Now I need to find a good power prolonger set for IG since getting extracts is a little more of a pain this time.