A comparative experiment on low aspect ratio (A ≈ 1.5) torusplasmas, including compact reversed field pinches (RFPs), spheromaks and spherical tokamaks (STs), has been performed in the TS-3 and TS-4 compact toroid (CT) devices.In particular, a compact RFP with q0 as large as 0.3 was found tohave a low n dynamo mode, n = 3, while a spheromak with q0 ≈ 0.5 had an n = 2 mode. Under OH current sustainment, the magnetic fluctuation and loop voltageof the CT were observed to increase inversely with its q value.A new method of edge current drive was developed using axial CT merging, which together with the OHcurrent drive created a balanced current drive.This current drive was found to reduce the dynamo fluctuationsof compact RFPs and spheromaks by a factor of 3. Multiple CT merging is a promising method of edge current drive because of its intermittent current drive and its detailed control of currentprofiles using varied size of colliding CTs.