2HP will do the trick. Go for inverter for power savings since 2hp is 1700 WATTS - 1900 WATTS depending on brands.

No, you cant use the same piping. A new piping is the only way.

Brand, depends on your budget. For China brand, Haier is good. For reputable brands, Daikin GA, Acson, Pana, Mitsu and Hitachi also good.

Outdoor size differs from Inverter and Non inverter. Outdoor unit for inverter bigger compare to Non inverter for Pana. The effect will be faster cooling for bigger outdoor. Why Pana use smaller outdoor for non inverter? Because want to cut cost.

Other brands not so sure.

Power consumption:
1700 watts - 1900 watts, depending on brands for non inverter. Same compressor  speed through out the operation.
High starting amp.
400 watts - 1980 watts, depending on brands for inverter. Different compressor speed through out the operation.
Low starting amp.

Bro your chances of having a bigger copper piping is close to zero. Because very seldom contractor will install copper piping size which is bigger than the intended size. why? Because bigger copper piping is costly and it is of no use to over size the piping.

However, to confirm it, call any air cond contractor u know, they will surely know the size for 2hp ac. Good luck to you

Your room need 2.0hp to support your room base on the measurement you provided. Since your old ac is Midea 1.5hp the piping should be size at 1/4 and 1/2 in inches and the thickness is confirm less than 0.61mm

Nowadays the piping for Daikin, Pana, ME or Acson in 2.0hp should be using the same measurement as the 1.5hp Midea but in terms of the thickness, mostly aircon man will suggest to replace the old piping with the new inverter piping cause the thickness is different (R410- 0.61mm) (R22- 0.51mm) so here's the trick, we know latest refrigerant needs at least 0.61mm to support the pressure but... If your piping is not concealed then I will suggest to replace entire piping. If your piping is concealed and don't wanna spend a big buck. Tell your aircon man to braze the 0.61mm piping near the indoor and outdoor joints. This trick is safe too and will not blown the joints if the technician is well experience in brazing.

Not to forget the piping need to do entire flush down with nitrogen. The oil in the old piping is very contaminated.

Your case is still have hope to replace a 2.0hp air con. You just need to find a right guy to do it.

Check the picture for the Midea 1.5hp and Pana 2.0hp piping size. Is actually to suit your needs. Just thickness different but it can be solve.

Bro, If your hitachi 1 hp ACs are still in good condition, let me know, i have a friend who buys used ACs.