@Andone :  Thanks for your input. We will likely try out this router.  I understand that 1024 theoretical limit and 100 practical  limit  is good enough for any small enterprise, where this product may be targetted at. However , a couple of  further probes questions:

(1) 1024 is a good enough pool for us for now and quite some time in future. If I understand what you are saying. the moment I set the DHCP server pool  (LAN Gateway address is 10.0.0.1 and subnet mask 255.0.0.0) as

       start address = 10.0.2.1 

       end address = 10.0.6.254

the TL-ER5120 V4 would not accept this and flag an error msg/popup saying the max limit is 1024 address. Same way as the TL-R480T+ V8 did on going beyond a pool size of 256.  Just won't allow a range bigger than 1024 to be configured in the first place Right ?

(2) Also what is the limiting factor for 100 clients ? We presently  understand that this may be the number of *simultaneous clients using the Router for Internet service,  and not the actual number of addresses allocated by pool  at any given point of time (dependant on lease period of DHCP). Is it  limit coming because the routing is CPU bound or memory bound ? I  observed that the V4 version of ER-5120 has bumped up the RAM from 512 MB DDR3 to 2 GB DDR3, so is it the CPU now ?

To some testing before deployment, yesterday night we built a pfSense Firewall Router  with a quad core J1900 Asrock Mobo, 8 GB RAM, 13  Gigabit NIC interfaces (3 quad-port Realtek cards, 1 onboard Realtek) using some salvaged old parts and initial testing indicates that it maybe able to handle LAN-WAN throughput of  800 mbps -1 Gbps max. But that machine is happy to let me configure a pool size way bigger than 1024 and I have no idea if it will crib if the number of simulatenous users goes beyond 100 or higher/lower number. We will not be using this in a deploymednt environment, beacuse of the learning curve for the system integrator handling our project.