The low option is no less hilly, though the climb is reserved to the end; nor less rural, though closer to the M25.
Shoreham village 0.5 is worth exploring, including diversions towards the river (and on to Shoreham, for services from Sevenoaks & Maidstone). The Darent opens up beyond its cut through the Downs, but Cycle Orbital is turning west; 2.5 Over the M25 and L for Chevening on a busy A224; the Pilgrim’s Way is unavailable until after Chevening House. At the left bend in the road 3.5, indicate R and take the bridleway to 4 Chevening Church (access rights unconfirmed but walkable in 5 minutes). L to skirt the Chevening estate (R at 4.4 and 4.8, also 5.3 – but L for Spinoff 5 link on track to Sundridge), until L 6 on Pilgrim’s Way proper.
You are far enough away from the M25 to enjoy the serenity of hillside views (Chalk escarpment to the N, Greensand dip slope to the S) and mixed farmland, including vineyards. There is a choice of climb back to the N Downs Way: 1] 8.4 Westerham Hill, then L off-road on The Avenue and Chestnut Ave; 2] 9.3 Clarks Lane (recommended for steady gradient and views); 3] 10.6 R Titsey Hill is steep and shaded but extends the Pilgrim’s Way experience (L Spoke 3 ext Oxted link). NB for rides into the Kentish Weald take any of the lanes south off this route; Spinoff 5 loop ‘returns’ 9.3 from Westerham.