Checking the onboard video of PSLV C43 gives a feel like the CubeSats are released in very proximity.
Does this mean that these CubeSats will be orbiting in such very close proximity through out their life?
At the moment of release from the dispenser on the launch vehicle or other carrier spacecraft the CubeSats will be very close.
After that they will start to naturally separate due to a variety of reasons:
After a while, the CubeSats will begin to disperse into different orbits. There is a chance of future recontact/collision, and the launch provider is supposed to run analysis to ensure that this chance is minimized.
This is not unsimilar to what happens when two space objects collide. Here instead of "deployments" you have debris being scattered by the collision. Check out this video that shows how the cloud of debris is first clumped together but then starts spreading out.
This excellent answer lists a number of different cubesat deploy mechanisms used on PSLV-C43. One could try to check each of their deploy velocities, my guess is that they will be in the ballpark of 0.5 or 1.0 meter/sec. Guessing 1 cubesat every minute,that's 30 to 60 meters from one to the next.
Watching the video PSLV-C43 / HysIS Onboard Camera View cued at
01:12 you can see that some cubesats are deployed prograde and the others retrograde. Looking at the image below one can see that there is a bimodal distribution of orientations (left and right, not radial). The spacecraft's axis was first oriented towards the nadir.
After several deployments the spacecraft pitched so that the deploy direction was towards the nadir instead of retrograde + prograde.
While 1 m/s might sound slow compared to 7700 m/s its plenty to space the satellites out. Since Earth's gravity field has both a ~part per thousand oblateness and other lumps, these orbits will tend to "scramble" (excuse the fancy science word) over time.