How can I set up my land so that prims can be assigned to renters without parceling ?

[TayTay Denimore]

Alternately, if the land is parceled the only way to add more prim is to use region/estate bonus multiplier correct?

[Silky Mesmeriser]

The only way to assign prims without parcelling is to use a scripted rental box, naturally that wont actually be able to stop people rezzing over their limit but they are able to send warnings to both you and the tenant and allow you to use your normal eviction proceedures if the tenant does not bring their account back into order within the time stipulated in your rental agreement.

As for the other question yes, the only way to change the prims on a parcel is to change the parcels size or to use the region/estate bonus.  Note however that when that is used the region can still only have 15,000 prims total so not all tenants will be allowed to use the additional prims it grants in effect what it does it allows some parcels to use more than their fair share by effectively taking those prims away from the fair allocation of other parcels within the sim which are using less.  As such prim bonus can only be done fairly where an area of land containing prim allocations at least equal to the bonus is kept devoid of prims and not rented to tenants, or uses lightly primmed landscaping.  For example having the centre 1/4 of the sim made into a lake with some low prim landscaping perhaps would fairly and sustainably support a prim bonus of around 1.20-1.24 (The other 0.01-0.05 or 150-750 prims being the prims for the landscaping).

[Storm Clarence]

I don't think you can assign prims individually without 'breaking' the parcel.

The only way to add more prims to parceled land is to buy more land.  if all your parcels are on the same sim the smallest of the parcel can use all the prims from all the parcels you own.  You must control the prims used by each renter to make sure they do not exceed the amount of prims you are renting to them.

[Knowl Paine]

You could create a Group. Inform renters what their prim limit is. This only works with a small Groups of established Residents and requires supervision.

If you own a whole region you want to parcel the land, Residents will want to have their names show as owner.

As mentioned the Bonus factor comes from land you subdivide and preserve as green space or other low prim detail to make the region inviting or to define bounderies.

Yes you are correct.