First you need to find out if you have a 32-bit or 64-bit machine. You can find out by typing the following in the windows File Explorer and looking at the System Type:
Control Panel\System and Security\System
Modern PCs with Windows 10 would be 64-bit machines.
DatacomServer15.0_R098255_x64 will install the 64-bit ODBC and JDBC drivers and can only be installed on 64-bit machines. This will be used by 64-bit applications running on the machine.
DatacomServer15.0_R098255_x86 will install the 32-bit ODBC and JDBC drivers and can be installed on both 32-bit and 64-bit machines. This will be used by 32-bit applications running on the machine.
On 64-bit machines you should install both the 32-bit and 64-bit drivers so that 32-bit applications and 64-bit applications can run on the machine.
Note that windows PTFs are cumulative so you only need to use the installers from the highest numbered published PTF.