I don't think that OHMSS was "low-tech" due to Connery's absence, it was more of a reaction to the creeping excesses of the two previous films.   Director Peter Hunt was a big fan of the original Fleming novels and he is on record saying he carried along a paperback copy of OHMSS (with his own holographic notations in the margins) throughout the filming of Bond no. 6.  The fantastic gadgetry of the Bond series was mostly an invention of the filmmakers, an extension of Fleming's interest in and knowledge of modern armaments and radios and such.