I have a very narrow strip of 'real estate' in the garden for my railway, but I still have a double track line and use R1/R2 curves, as can be seen here.
However my locos are Euro NG and the largest are the Bo-Bo V51/52 or 2095 Whizzy Cranks. Similarly, most of my wagons are 2 axle, or shorter bogie vehicles. All LGB stock
should go round R1.
If you can accept these limitations then R1/R2 work fine, but if you plan to run US, or Euro SG like the Piko 218, or the Class 66 in the future, then LGB R3/Piko R5 (4 ft radii) should be your minimum....