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I would like to ask if the Nvidia 2070s would fit into S20 tower since its 6-7cm longer than 1050ti which I currently have, I have 650W PSU which is  recommended by  Nvidia and my PC specs are Xeon w3520, 12gb ram, 512SSD, 2TB HDD, 650w PSU.

I  would like  to  know would this PSU really be enough for the 2070s and if  the card fits into S20 Tower ?  

Edit:

I checked  again and the PSU is 625W with max usage of 610W , the  test  I made with  my specs shows the usage is 599W usage if I have 2070s installed, would this cause problems?

This is a bit of a loaded question and not as straight forward to answer as one might think.

First, I'll state the S20 doesn't officially support any GeForce cards.  That's a standard statement for the platform, but I have to put it out there.  Many users  have been successful in getting GeForce cards to function just fine in S20, but no guarantees.  

We actually don't have any of the 2070 reference design cards (Founder's Edition) in house.  However, the reference card design length should fit just fine in S20 as it's designed to handle standard full length GPUs.  Typically you don't see a ton of variability in length from vendor to vendor, so I doubt length will be a concern.  The other dimensions, namely width and height, can vary greatly from vendor to vendor, so there's really no way for us to evaluate that without knowing which specific card you're looking at.  Again, reference design dimensions should be OK though for width and height as well.

From a power standpoint, this is something we'd probably have to set up and test.  Again, cards will vary, but the reference design is generally 175W-185W TDP for that GPU (could go quite a bit higher if USB-C is also supported).  Overall the TDP isn't an issue as S20 was designed to support GPUs up to 225W TDP if I remember correctly.  However,  as  that card uses a single 8-pin connector, that's going to put the entire aux 12V power load on a single rail.  This is where I think there could be potential problems.  The normal power spec should be OK, but there's an input EDP (surge) power spec associated with those cards that the S20 power supply wasn't really designed to handle.  Keep in mind that power supply was designed upwards of 12 years ago.  There's a chance the input EDP current could be high enough, for a long enough period of time while under load where the PSU will go into over-current mode and shut itself down to protect itself.  

We can try to test this out with the 2070 samples we have (which are close to the Founder's Edition I believe) to give you an idea.  But in reality your scenario might be different since you most likely have a different GPU.  Still, it should be enough to give you an idea of where you are in terms of support.

The alternative here would be to consider replacing the power supply with a newer (3rd party) PSU design.  Newer PSU designs have started to take this surge current into account and they are able to handle the power loads much better.