That depends on what you mean by "on top" and what kind of levers you have.

Riding with your hands on top of a road bike's brake levers, "on the hoods" of the levers, is pretty much the standard hand position on a road bike. (A Google image search for "on the hoods" will give you plenty of examples.) Modern levers are designed to be grasped and pulled from that position. It works well and is comfortable with pretty much any lever made in the last few decades.

On the other hand, if "on top" means from the flat part of the handlebar near the stem... The old-style lever extensions that let you brake from there generally did provide poor braking performance. Those lever extensions earned some derisive nicknames like "suicide levers" or "turkey levers". There could be play in the pivot and the extensions were flexy, leading to weak braking and a mushy lever feel.

The modern equivalent to those "turkey levers" are interrupter levers, which are a lot like the levers in the link you posted above. Unlike the old turkey levers, interrupter levers work really well. You can install them in addition to regular road bike brake levers, so you can brake from the hoods, the drops, or the flats. The one catch is that your regular levers have to be 'aero', meaning the cables get routed under the handlebar tape. If your old levers are non-aero, you'd need to replace them to use them with interrupter levers.

Interrupter levers like Tektro RL720 levers sell for about $20-25 per pair. If you need to buy a set of aero levers to pair them with, a set of comfy Tektro RL340 levers costs about the same. Beyond the levers, you'd just need brake cable, housing, and handlebar tape.