If you open a HTB ISA in the next few days, with the £1000 deposit and the normal limit of £200 per month, you can transfer that ISA into the new Lifetime ISA (after April 5th?) and then still deposit another ~£4200 into the Lifetime ISA over the financial year.
There are positives and negatives to the HTB and Lifetime ISAs, including...
Lifetime isn't available to those over 40, even if they've never owned a home
Maximum topup by government is £4000 for HTB and IIRC, a whopping £32000 for Lifetime
HTB is limited to £200 per month, with Lifetime you deposit the whole year's allowance in one hit
HTB is limited to £2400 over the year (excluding initial £1k opening deposit), Lifetime has limit of ~£4200 IIRC
You could use your HTB to help buy your first home within ~3 months of opening, Lifetime has to be open 12 months to get the government topup