Yupp, you can have more than one demat account, and there's no harm in it.
Ind Money is a one-stop destination to track and manage most of your investments, including US Stocks, Indian Stocks, Mutual Funds, PF, NPS, FDs, Credit Cards, and Insurance. It's one of the best investment apps available, but the risk might lie in its smaller scale compared to top brokerage apps in India. However, it's a top contender when it comes to US Equity Investments. I am personally using IND Money along with AngelOne(my first brokerage app) for investments and tracking purposes.
Note: Always make your Financial Decisions based on your own Risk Appetite and DYOR.