"All models have two M.2 slots that can either be used with mSATA-SSDs or NVMe-SSD"

No. The P70 has a m.2 NVME slot and a m.2 NGFF slot. Physically they are the same but NVME is PCIe; NGFF is SATA3.

It does NOT have an mSATA slot, an older and different and physically wider standard than NGFF, though both are SATA3.

NVME and NGFF slots are NOT interchangeable. The P70 will not take two NVME cards, and it will not take two NGFF cards. You get one of each. If you put a NVME card in the NGFF slot it will physically fit fine but do nothing. Same is true of a NGFF card in the NVME slot.

i can see a picture where the additional ssd disk is installed in the main bay in the laptop without any brakes or tray. Is it how the ssd disk suppose to be installed in p70?

http://www.notebookcheck.net/fileadmin/_processed_/csm_Thinkpad_P70_DSC00879_1de52f4d2b.jpg

When you insert the disk it feels very loose. There is plenty of space at the back (towards the bottom edge of the laptop) and the disk can simply slide back. There are is nothing  in the bay/chassis  that holds the disk in place.

The same applies to the space on the left and right of the disk. The disk can easily move vertically as there is nothing to hold the disk in place.

Anyone can share some comments.

ps.
Ive created this post here as well to clarify this situation.

https://forums.lenovo.com/t5/ThinkPad-P-and-W-Series-Mobile/disk-bracket-for-p70-to-install-SSD-disk/m-p/3307233#M58573

Thanks for the detailed professional review.
If anyone is interested in using this laptop with linux, I wrote a lot of notes and my own review here: https://docs.google.com/document/d/1GnyBE1xc4qx3EF-IcUOwr7d9D8Npzy63Pwj-joOw86o/edit#
Best, Marc

Why the grade discrepancy between the English and the German review (89 % and 91 % total score, respectively)?

WARNING: The reviewer notes in a couple of places that Windows 7 users might be better off getting the P70 with a lower-resolution FHD panel. After the review was written, however, Microsoft announced that on most Skylake systems only Windows 10 will be supported. The P70 is on a small list of Skylake-based laptops that will continue to get Windows 7 security updates until 20 July 2017, which is still only 18 months from now and two and a half years before Windows 7's end of life on 14 January 2020. Accordingly:

(1) Users who definitely want to be able to use Windows 7 until its end of life on 14 January 2020 might be better off buying a slightly older mobile workstation with a Broadwell (or earlier) chipset.

(2) Users who buy a P70 to run Windows 7 on should anticipate that they will stop getting Windows 7 security updates on 20 July 2017 and that they may feel compelled to upgrade to Windows 10 (or switch to Linux) sometime before that happens. This may affect their decision as to what kind of LCD panel to order their P70 with.

PWM at such low frequency

Lenovo and display quality again. It must be on purpose :( Oh yes, cutting costs matters.