Your 2k time seems ok for your weight and height: 2.8 W/kg.
The erg aground is for tall massive people who are not penalised by the slack at the catch, which is 20-30cm. For shorter people, this cannot be compensated just by rating faster, overrreach or by using higher drag, all carry extra costs. You'll do relatively better afloat if you have a quick catch, and a dynamic erg or slides can help aground. Double sculls and quads should be great fun, you can use your skills and agility and the boat and blades can be geared to suit.
74y, 188cm, 88kg, MHR 170. 3km/h in water, 10km/h on. Last 2k (2-15) 8.07@25