What is best possible manual tool for deweeding, esp like garden hoe?
The weeds and grass needs to be removed for making a garden patch for flower bushes and roses. The weeds are not tall or thick but needs to be removed. Even grass to be removed. The soil is more on clay side and is little tough for digging etc.
Go to a garden tools website and look at your options. There are many and every gardener has his/her favorite. Cobra head and Cap Cod weeders are popular. There are many types of shovels for loosening the soil so you can get out the weed's entire root system. Even hoes come in a variety of shapes. A good pair of nitrile gloves is also helpful.
A choice of weeding tool or combination of tools kind of depends on your physical ability and preference. How heavy a tool can you handle? How big is your plot? Can you swing a heavy maddock all day? You have described the conditions well, and I think a tool that is too light, like a common hoe, will not do the job of turning heavy clay soil to loosen the weeds and grasses.
My choice would be a pick-maddock or axe-maddock as the primary digging tool. With a good overhead swing and plunging of the wide blade, you will get some penetration, and then lift out the chunk of soil to be broken up and weeded. A steel rake and a lighter hoe can be used to break up the clods of clay in order to enable hand pulling/separating the grass/weeds from the soil. The rake can also be used to smooth the soil grade. I would also have a long handled shovel on hand to slice and beat and break clods apart.