One IP address for two wireless routers

You would have an IP conflict and nothing would work

What exactly are you trying to do here? Have a wireless network large enough to cover an entire area? You'd have to connect one router to the other, unless you're trying to use the second wireless router as a repeater or an access point. If you don't do access point mode on the second when it's wired to the first, hosts on each router won't be able to communicate with each other.

You can have a wired router connected to your modem, then have wireless routers configured as access points connected to it. That would make sense as well.

Let's call them Wireless Router A and Wireless Router B.

You'd plug the cable modem into Wireless Router A and then you'd plug Wireless Router B into Wireless Router A (but you wouldn't plug it into the WLAN port... just into one of the LAN ports).

Clients connected to Wireless Router B would get DHCP address from wireless router A (assuming that you've configured DHCP) and both clients connecting to either Wireless Router would be on the same IP subnet.

The downside of the config?  Nothing really, if that's what you need to do there aren't too many ways to do it.  If Wireless Router A dies then no one has internet access (you'd have to plug Wireless Router B into the cable modem).

If you want each of the Wireless Routers to be on a different IP subnet, it's slightly trickier.  You'd need to plug Wireless Router B into the WAN port of Wireless Router A and configure the WAN connection on Wireless Router B appropriately (with an IP in Wireless Router A's Range that's set as  static connection).

looking to your question if you put the same ip address to 2 Wireless router it will do ip conflict and any one of you of you ap will not work about the ssid you can create different ssid on each router as if you are using Cisco AP then you can create 16 different ssid with each having different Web key, but only the ssid which you want to broadcast will be displayed rest you have to configure on the user side with the ssid which you want them to connnect to.
YOU CANNOT USE SAME IP ADDRESS ON NETWORK DEVICES UNLESS YOU HAVE LOAD BALANCING ENABLE WHICH IS ONLY IN SERVERS.

if router B is connected to router A via LAN ports, would router B's static ip address need to be outside router's A IP address range? What would be the benefit of two IP subnets by connecting router A's LAN port to router B's WAN port?

What would be the benefit of two IP subnets by connecting router A's LAN port to router B's WAN port?
NONE, nothing NADA, NETWORK CRASH OF THE WORST KIND.

You can not connect 2 devises to one cable modem. The modem has a WAN port and a LAN port. It may have a built in switch but that is a different device.

What eactly are you wanting to do. What networking gear do you have?
momen switch router etc...