Gsus4 - self-discovered tip

There are advantages to playing the G chord with both fingerings , I learned an alternate fingering when I was a boy , thumb on the 6th string and index on the 1 string. I play it most of the time with the 2,3,4 fingering and recommend it to beginners , but I practice the 1,2,3 fingering because it has it's advantages to. It does take some practice to try and teach them hard headed fingers to use the fingering your brain is telling it use

I find the 2,3,4  fingering is easier for me to embellish the G chord  than the other, but for some songs the 1,2,3 is better.

Way back when I  was teaching myself the chords I found the  2,3,4 easier + it was a quick drop to C, F and D.  I rearly use the 1,2,3 unless Im playing Every Rose Has Its Thorn since its mostly G and G6sus4 (or C major with out the index) or I Hear the Music D and G.  Come to think of it, I dont even think about it now, i just go for what is more comfy with the changeout.

C major 7

I play Every Rose ... from time to time as well.  It was one of the first songs I got serious about learning because it is fairly easy to play and because my wife likes it.

I've never used a Cmaj7 but try this and see how it sounds to you:

In the verses and first part of the chorus, when you are alternating between G and "C", try alternating between these two:
  -  G as: 320033 (add that extra D on the B string)
  -  C (something) as:  x32033 (keep fingers 3 and 4 anchored from the G and move fingers 1 and 2 to the C position on the A and D strings).

I like the sound of that.  Everywhere else in the song I just use an open G and C.

Re Every Rose, I play it as you wrote it above. That's a C add 9. The third fret on the b string is a D, which is the 9 you're adding. Regarding the Dm7/G, your voicing is correct! How it sounds depends upon how you use the chord. In fact, a lot of chords change texture depending upon how they're used.

Example: My band plays a lot of blues-based rock and funky stuff. Our bass player is really active so I don't have to play full chords. I mostly play thirds, sevenths, ninths, and other chord extensions and let him handle the bass note. He can move from bass note to bass note and change the chord without me changing any notes at all, or more frequently with me just changing one note.

To hear an easy example of how this sounds, play this:

x
5
5
5
x
x

That probably sounds like C major to you. So put the C in the root to define the chord as C Major:

x
5
5
5
3
x

Now play this:

x
5
5
5
x
5

That's an A minor 7...which from theory you know is the relative minor of C. The point being you don't have to change notes to change chords. Cool, but motion to a relative minor being a bit too easy, let's do a tougher one.

I play this in Use Me by Bill Withers (chord tone names added for reference):

Em7
x
12 (5)
12 (b3)
12 (b7)
x
x

A7 (with a 9 added for fun):

x
12 (9)
12 (b7)
11 (3)
x
x

So just by changing one note I go from Em to A7, which is a i-IV progression.

Word to your business trip.

I just play Em7 to A7 but I use a few different voicings. I'm on a business trip but as soon as I get back I'll tab a few out for ya.

Here ya go Norm. Some Em7 voicings (with extensions):

12 (or 14 or 15)
12
12
12
x
12
----
7 (or 9)
8
7
9
7
x (or 0)

0 (or 2 or 3)
0
0
0
2 (or x)
0
---
3
3
4
x
x
x (or 0)
---
7 (or 9)
7
7
5
7
x

Some A7 voicings (with extensions):

First one is my favorite.
x
7
6
5
x
5
----
5 (or 7)
5
6
5
7
5
---
12 (or 14, or x)
12 (or 13 if x above)
12
11
12
x
---
I also play lots of portions of these chords, mostly 3rds and b7s, eg:
x
x
6
5
x
x

and

x
x
12
11
x
x