I have some inconsitences in order to atake into acount the effect of pressure in a high pressure system.

CASE 1 (OPE) W+T1+P1
CASE 2 (SUS) W+P1
CASE 3 (SUS) W
CASE 4 (SUS) P1
CASE 5 (EXP) L5=L1-L2
CASE 6 (OPE) L6=L4+L5
CASE 7 (OPE) L7=L1-L3

The bourdon pressure effect is active for translation only

I have found inconcistences between the loads reported for cases 6 and 7 (they should be similar); then for example for case 2 it is reporting displacements that are not reals.

2300 Rigid ANC
1 OPE 818. 15679. 7581. -4939. -1410. 902.
2 SUS 70. 15209. 1560. -4874. -69. 178.
3 SUS 2. -2662. -75. -2355. 141. -585.
4 SUS 276. 358. -219. -50. -514. 170.
5 EXP 749. 471. 6021. -64. -1342. 725.
6 OPE 1025. 828. 5802. -115. -1856. 894.
7 OPE 816. 18341. 7656. -2584. -1552. 1487.

No, I disagree. Superposition does not necessarily apply to piping systems - especially if there are non-linear boundary conditions or friction in the model.

So, I agree with your case #7, whereas case #6 may yield similar results only for a linear job. In general, I would not rely on your case #6.