Whatever part of the holy Quran one wants to recite, he may recite and can do isal-e-sawab. If a person does isal-e-sawab by reciting the whole Quran then it is too lawful rather it is better. The more one recites the more reward he shall gain. But the ongoing method of Quran khawani is makrooh in which people get together in a fixed date and recite the holy Quran. One should avoid it. One should recite and do isal-e-sawab individually without the specification of date and time.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband