Are 19th century testaments different from those of preceding centuries?

Yes, the 19th century saw changes in the format and character of testaments. Until 1824 testaments were confirmed by commissary courts, but after that date they became the responsibility of the sheriff courts. So inevitably there were some changes. But even before 1824 you may notice some differences. These came about as a result of clauses in the Revenue Acts of 1804 and 1808. Briefly, separate registers of inventories, confirmations and settlements (wills) were kept, and it was possible for an executor to register an inventory with the court without seeking confirmation. And, of course, you should find 19th century testaments much easier to read.