Guitar Amp on SP-404 MK 2 - How useful for (new) players? 

this is such a cool device

I wish Roland would add a Bass amp

Oh why never knew the SP 404 MK2 had guitar amp stuff! So cool! I need to sample my guitars into it.

Guitar + FX is awesome 🔥🔥🔥

Perhaps a stereo DI Box would help with guitar amp sim buzzing. I will experiment soon.

I also plan on trying a real tube amp with a two notes attenuator/speaker IR.

I had the grounding problem running guitar thru a USB powered Zoom H4n and discovered if I plugged a USB data cable from Zoom into the desktop computer port, that would ground the guitar. i.e. USB direct power sources (I got a power cable for that) may be two prong from the wall. Computer is 3 prong and everything is grounded. I'd guess that plugging USB into a spare port on a PC monitor would accomplish this too.

what do you think about the available vocal fx>?

Bass Amp?

Can one use the effects in real time on the gtr or just applied after the gtr sample is created?

Preamp yes, definitely not an amp. You cant plug in speakers into it without an actual amp in between.

I’d say those guitar effects are shitty.