
Shure
SM58
Indestructible live workhorse; but muffled for studio vocals.

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The thing about condenser mics are just not true. You just need to put it at the right place in your room and treat your room a bit (you don't even need to make it 100% soundproof you could go with just a few wood-wool panels in one corner and point the back of the mic towards the free space in your room - where most people would also have furniture that can work as sound absorbing material). It's actually way more important to put your mic at the right place and treat your room rather than what mic you got. Also, a cardioid condenser mic isn't supposed to pick up sound waves from behind the mic, so if you're experiencing this issue you're either placing your mic wrong or got a REALLY shitty room - or both.
Nope. Most people will have lots of furniture in their rooms that can act as sound absorbing material, providing a decent amount of reduction from reflection and absorb the sound waves. You don't need to even put up any kind of panels if you know how to place your mic and mix your vocals. Also consider that lots of professional vocalists produce great songs in hotel rooms with little to zero equipment - Russ, Tinashe and many others are examples.
USB mics aren't really meant for quality vocal production, but Rode NT-USB+ could be one of the better USB options. However, I would rather recommend either: Lewitt LCT 440 pure or Rode NT1 with a Focusrite Scarlett Solo interface or something similar (the 3rd gen would do just fine). Also consider that he might need a mic stand and XLR cable Make sure to NOT point the mic directly towards walls but rather towards free space or a lot of heavy furniture - especially in a untreated room. Don't buy sound panels cause they are shit and will only reduce reflections NOT absorb sounds - i.e. when you want to make your room more sound proof, you want dense materials like wood or cement-bonded wood wool (way better than those plastic panels you're talking about, and those wood wool panels are actually affordable)
Dude just get a rode nt USB+ or an AT2020 USB both under 200 bucks and sound fantastic. No interface needed since they are USB mics and less hassle. I have a blue spark xlr and sound quality wise I can't tell the difference between it and my rode nt USB. The only difference is that the blue sounds warmer than my rode.
Rode NT USB works wonders, I use it all the time
Volume issues? Sure it's not a user angle? Are you solely using their software or do you use filters in OBS aswell? I'd scrap the software and focus on filters to adjust things. Other then that Rode NT is a solid mic, i've had the USB one myself for years.
Personally I will vouche for the Rode NT USB mic. It's roughly $140 on Amazon right now from what I saw. Yes it's a USB mic and while it sound great out of the box, with some simple OBS filters you can make it sound absolutely crisp!
The NT USB is a good alternative. Same cartridge from what I understand. But a limited bid depth and sample rate. So it depends if you have an audio interface or not.
3 months ago I bought the Rode NT usb-c. For recording with iphone or iPad, excellent sound and easy setup (plug and play usb c, no power cord)

Shure
SM58
Indestructible live workhorse; but muffled for studio vocals.

Shure
SM57-LC
Versatile for instruments; needs pop filter for vocals.

DJI
Mic 2
Unbeatable convenience, 32-bit float; but poor Bluetooth audio.

Samson Technologies
Q2U USB/XLR Dynamic Microphone with Accessories
Great value dual USB/XLR; recent price increase noted.

Shure
SM7B Vocal Dynamic Microphone
Professional vocal sound; but expensive, needs external amplifier.