It should be a soft top convertible.
luxury automakers don't really use soft tops unless its an entry level convertible... and even then that still doesn't seem to happen don't expect to see a soft top on a lexus especially.
I don't know why you come to such conclusion. Hardtops are usually cars with small roofs, and usually entry level cars. Here a list:
Hard top (including stopped production):
Peugeot 207 CC (no more successor)
Peugeot 308 CC (no more successor)
Nissan Micra C+C (no more successor)
Renault Wind (no more successor)
VW Eos (no more successor)
Mazda MX-5
Ferrari California
Mercedes SL (successor with soft top)
Mercedes SLK (successor likely with soft top)
BMW Z4 (successor likely with soft top)
BMW 4er Convertible (successor with soft top)
Lexus IS C
Volvo C70 (no successor)
Opel Astra Convertible (no more hard top)
Ferrari 488 GTS
McLaren 650
Soft-top
BMW 2 Series
BMW 6 Series
Audi TT Roadster
Audi A5
Mercedes C Convertible
Mercedes E Convertible
Mercedes S Convertible
Porsche 911 Convertible
Bentley Continental GTC
Rolls Royce Drophead and Gost Convertible
Hard-top or soft-top does not indicate premium or not. On a longer roof, soft top looks better, on a short roof, hard-top is more practical but also heavier.