The closest 4* hotel to Varadero Town that we dare to recommend is Cuatro Palmas Hotel. This one is towards the end of the Town so you can walk any where. Apart from Cuatro Palmas hotel there is no other decent enough 4 star hotel that is worth recommending. The international Hotel one of the oldest 4 * hotels in Varadero is walking distance from the Town.
Sol Sirenas Coral , Breezes Varadero, Sol Palmeras, Melia Varadero are the closest most decent 4 star hotels to the Town of Varadero but I would not say they are walking distance though. You will have to take a taxi but taxis in Varadero are very cheap. There are shuttle buses from this hotels to Town anyway and it is free.