My system is BXi5-4570R and I am using latest OpenCore 0.6.3 with modified DVMT pre-allocated and total GFX memory settings through modGRUBShell.efi.
Here is the table for all the settings from BIOS:
DVMT Pre-Allocated, VarStoreInfo (VarOffset/VarName): 0x30A
DVMT Total Gfx Mem, VarStoreInfo (VarOffset/VarName): 0x30B
0x36790 One Of: DVMT Pre-Allocated, VarStoreInfo (VarOffset/VarName): 0x30A, VarStore: 0x1, QuestionId: 0x262, Size: 1, Min: 0x0, Max 0x0, Step: 0x0 {05 A6 BF 04 D1 04 62 02 01 00 0A 03 10 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00}
0x367B6 One Of Option: 32M, Value (8 bit): 0x1 (default) {09 0E C0 04 30 00 01 00 00 00 00 00 00 00}
0x367C4 One Of Option: 64M, Value (8 bit): 0x2 {09 0E C1 04 00 00 02 00 00 00 00 00 00 00}
0x367D2 One Of Option: 96M, Value (8 bit): 0x3 {09 0E C2 04 00 00 03 00 00 00 00 00 00 00}
0x367E0 One Of Option: 128M, Value (8 bit): 0x4 {09 0E C3 04 00 00 04 00 00 00 00 00 00 00}
0x367EE One Of Option: 160M, Value (8 bit): 0x5 {09 0E C4 04 00 00 05 00 00 00 00 00 00 00}
0x367FC One Of Option: 192M, Value (8 bit): 0x6 {09 0E C5 04 00 00 06 00 00 00 00 00 00 00}
0x3680A One Of Option: 224M, Value (8 bit): 0x7 {09 0E C6 04 00 00 07 00 00 00 00 00 00 00}
0x36818 One Of Option: 256M, Value (8 bit): 0x8 {09 0E C7 04 00 00 08 00 00 00 00 00 00 00}
0x36826 One Of Option: 288M, Value (8 bit): 0x9 {09 0E C8 04 00 00 09 00 00 00 00 00 00 00}
0x36834 One Of Option: 320M, Value (8 bit): 0xA {09 0E C9 04 00 00 0A 00 00 00 00 00 00 00}
0x36842 One Of Option: 352M, Value (8 bit): 0xB {09 0E CA 04 00 00 0B 00 00 00 00 00 00 00}
0x36850 One Of Option: 384M, Value (8 bit): 0xC {09 0E CB 04 00 00 0C 00 00 00 00 00 00 00}
0x3685E One Of Option: 416M, Value (8 bit): 0xD {09 0E CC 04 00 00 0D 00 00 00 00 00 00 00}
0x3686C One Of Option: 448M, Value (8 bit): 0xE {09 0E CD 04 00 00 0E 00 00 00 00 00 00 00}
0x3687A One Of Option: 480M, Value (8 bit): 0xF {09 0E CE 04 00 00 0F 00 00 00 00 00 00 00}
0x36888 One Of Option: 512M, Value (8 bit): 0x10 {09 0E CF 04 00 00 10 00 00 00 00 00 00 00}
0x36896 One Of Option: 1024M, Value (8 bit): 0x11 {09 0E D0 04 00 00 11 00 00 00 00 00 00 00}
0x368A4 End One Of {29 02}
0x368A6 One Of: DVMT Total Gfx Mem, VarStoreInfo (VarOffset/VarName): 0x30B, VarStore: 0x1, QuestionId: 0x263, Size: 1, Min: 0x0, Max 0x0, Step: 0x0 {05 A6 D2 04 D3 04 63 02 01 00 0B 03 10 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00}
0x368CC One Of Option: 128M, Value (8 bit): 0x1 {09 0E D4 04 00 00 01 00 00 00 00 00 00 00}
0x368DA One Of Option: 256M, Value (8 bit): 0x2 (default) {09 0E D5 04 30 00 02 00 00 00 00 00 00 00}
0x368E8 One Of Option: MAX, Value (8 bit): 0x3 {09 0E D6 04 00 00 03 00 00 00 00 00 00 00}
0x368F6 End One Of {29 02}
My current settings are:
setup_var 0x30A 0x04
setup_var 0x30B 0x03
Attached is EFI folder with blank SMBIOS settings. Fill in your own.