Is EF-M mount worth investing for a new user

First, to clarify, there are two primary types of screens; "fully articulated" and "tilting". Your FZ1000 would be the "fully articulated" type with the hinge on the side of the camera. "Titling" screens are hinged at the top and/or bottom.  "Flip" and "tilt" are often used interchangeably.  "Fully articulated" is also referred to as a "swivel" screen.  Things get even more confusing when you throw a screen like that on the Z9 into the conversation.

The M50 and M50 II employ "fully articulated" screens. All of the other M cameras use tilting screens, except for the original M and M2 which have fixed screens.

Whether or not an older model is worth buying will depend a lot on your personal needs and intended use.

• The M, M2, and M10 all use the much older 18mp sensors and produce the lowest image quality of the lineup. AF is only suitable for stationary subjects.
• The M3 uses an older 24mp sensor that is a step behind the newer models for image quality and the AF is also only really suitable for stationary subjects.
• The M5, M6, M100, M200, M50, and M50 II all use the same 24mp sensor which produces good image quality. AF is decent on the M5, M6, and M100. The M200 and M50 have better AF, and the M50 II has the best AF of this group
• The M6 II uses the newer 32mp sensor and has the best image quality and the best AF of the bunch.

If you are capturing video, only the M6 II offers decent 4k with good AF. The rest of the lineup is pretty lousy for video, by today's standards, and you would be better off capturing video with a smartphone.

Coming from m4/3, this may, or may not, be an issue for you.  None of the M system cameras have IBIS and nothing is weather sealed.  There are 5 zoom lenses with stabilization and the 28mm f/3.5 macro is also stabilized.  None of the other prime lenses will be stabilized.

Is the Canon EF-M still going strong?  No.  In 2018, Canon had 4 different bodies for sale.  In 2020 it was three bodies.  In 2022, the M6 II was discontinued and the lineup is down to just 2 bodies.  The last new lens was launched in 2018.  If the system has everything you would want right now, it could be a good value.  However, don't expect any new bodies with significantly upgraded features, or any new lenses.  By all appearances, Canon is slowly phasing out the EF-M system and is in the process of replacing it with the new crop RF-S system.